Publisher Summary This chapter focuses on the adult pulmonary surfactant system and the effects o... more Publisher Summary This chapter focuses on the adult pulmonary surfactant system and the effects of aging process, respiratory diseases, and environmental factors on it. While very few studies have investigated the effect of aging on the pulmonary surfactant system, some evidence indicates that changes in surfactant may ameliorate the negative aging effects on lung architecture and function. Furthermore, aging has other effects, which could contribute to the effects of aging on surfactant composition, function, and regulation. Particularly, the autonomic nervous system; the immunological status of the lung such as numbers of alveolar macrophages, leukocytes and neutrophils, extent of phagocytosis, concentration of inflammatory mediators; and alveolo-capillary clearance all change with age and could impact on the composition and function of the surfactant system. The most common, serious surfactant-related disease is the acute respiratory distress syndrome (ARDS), in which pulmonary surfactant function is severely impaired, contributing to the high mortality rate of this disease. Major imbalances in total protein as well as surfactant-specific proteins occur during the progression of ARDS. Total protein is always markedly increased, due to the influx of plasma proteins, which exacerbates the poor surfactant function, as plasma proteins directly interfere with the surface tension lowering ability of the surfactant film. Impaired surfactant function, attributable to increased plasma protein leakage, has been demonstrated in animal models of asthma and in BAL fluid of asthmatic patients.
Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to ... more Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to negate the detrimental effects of oxidative stress on lung maturation. Antioxidants improve respiratory function in postnatal life and adulthood. However, the outcomes and biological mechanisms of antioxidant action in the fetal lung are unknown. Methods We investigated the effect of maternal daily vitamin C treatment (200 mg/kg, intravenously) for a month in late gestation (105–138 days gestation, term ~145 days) on molecular regulation of fetal lung maturation in sheep. Expression of genes and proteins regulating lung development was quantified in fetal lung tissue. The number of surfactant-producing cells was determined by immunohistochemistry. Results Maternal vitamin C treatment increased fetal lung gene expression of the antioxidant enzyme SOD-1, hypoxia signaling genes (HIF-2α, HIF-3α, ADM, and EGLN-3), genes regulating sodium movement (SCNN1-A, SCNN1-B, ATP1-A1, and ATP1-B1), sur...
Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to ... more Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to negate the detrimental effects of oxidative stress on lung maturation. Antioxidants improve respiratory function in postnatal life and adulthood. However, the outcomes and biological mechanisms of antioxidant action in the fetal lung are unknown. Methods We investigated the effect of maternal daily vitamin C treatment (200 mg/kg, intravenously) for a month in late gestation (105–138 days gestation, term ~145 days) on molecular regulation of fetal lung maturation in sheep. Expression of genes and proteins regulating lung development was quantified in fetal lung tissue. The number of surfactant-producing cells was determined by immunohistochemistry. Results Maternal vitamin C treatment increased fetal lung gene expression of the antioxidant enzyme SOD-1, hypoxia signaling genes (HIF-2α, HIF-3α, ADM, and EGLN-3), genes regulating sodium movement (SCNN1-A, SCNN1-B, ATP1-A1, and ATP1-B1), sur...
American Journal of Respiratory and Critical Care Medicine, 1994
We have tested the hypothesis that the composition of alveolar surfactant varies with pattern of ... more We have tested the hypothesis that the composition of alveolar surfactant varies with pattern of breathing and level of fitness. We examined three major components of surfactant, surfactant protein A (SP-A), disaturated phospholipids (DSP), and cholesterol (CHOL) in bronchoalveolar lavage (BAL) fluid from 12 healthy men before and after exercise. Fitness was assessed as work load/heart rate ([kpm.min-1]/[HR.HRmax-1]) achieved during cycling for 30 min at 90% theoretical maximal heart rate. Using a bronchoscope, four 20-ml vols of 0.15 M NaCl at 37 degrees C were instilled and then recovered from first a right upper and then a right lower lobe segmental bronchus. As we found no differences in the BAL from upper and lower lobes, the fluid was combined. We found a direct relationship between CHOL and DSP (rs = 0.84, p < 0.001), SP-A and CHOL (rs = 0.40, p < 0.025), and between SP-A and DSP (rs = 0.44, p < 0.025). The change in the ratios CHOL/DSP, SP-A/CHOL, and SP-A/DSP immediately after exercise was correlated with fitness (rs = -0.56, p < 0.025; rs = 0.75, p < 0.005; rs = 0.62, p < 0.025, respectively). We conclude that the composition of surfactant can change rapidly with exercise in a manner related to fitness, and we suggest that this is consistent with the existence of at least two pools of tissue surfactant of different composition supplying the alveolar compartment.
Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurologica... more Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurological and skeletal pathologies. Respiratory dysfunction is a secondary pathology contributing to mortality in MPS IIIA patients. Pulmonary surfactant is crucial to optimal lung function and has not been investigated in MPS IIIA. We measured heparan sulphate (HS), lipids and surfactant proteins (SP) in pulmonary tissue and bronchoalveolar lavage fluid (BALF), and surfactant activity in healthy and diseased mice (20 weeks of age). Heparan sulphate, ganglioside GM3 and bis(monoacylglycero)phosphate (BMP) were increased in MPS IIIA lung tissue. There was an increase in HS and a decrease in BMP and cholesteryl esters (CE) in MPS IIIA BALF. Phospholipid composition remained unchanged, but BALF total phospholipids were reduced (49.70%) in MPS IIIA. There was a reduction in SP-A, -C and -D mRNA, SP-D protein in tissue and SP-A, -C and -D protein in BALF of MPS IIIA mice. Captive bubble surfactometry...
Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth r... more Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth restriction that may influence respiratory outcome at birth. We investigated the effect of maternal chronic hypoxia for a month in late gestation on signalling pathways regulating fetal lung maturation and the transition to air-breathing at birth using isobaric hypoxic chambers without alterations to maternal food intake. Maternal chronic hypoxia in late gestation increases fetal lung expression of genes regulating hypoxia signalling, lung liquid reabsorption and surfactant maturation, which may be an adaptive response in preparation for the successful transition to air-breathing at birth. In contrast to other models of chronic fetal hypoxaemia, late gestation onset fetal hypoxaemia promotes molecular regulation of fetal lung maturation. This suggests a differential effect of timing and duration of fetal chronic hypoxaemia on fetal lung maturation, which supports the heterogeneity observe...
Administration of glucocorticoids (GCs) to women at risk of preterm delivery reduces the newborn&... more Administration of glucocorticoids (GCs) to women at risk of preterm delivery reduces the newborn's risk of respiratory distress syndrome (RDS) by 35% to 40%; however, not all infants respond to this treatment. Fetal growth restriction (FGR) increases the risk of prematurity, perinatal morbidity, and mortality. This review aims to synthesize current evidence reporting the difference in RDS risk between FGR and normally grown infants (Question 1) and whether antenatal GC administration reduces the risk of RDS morbidity in FGR infants (Question 2). Systematic searches were performed, and after screening, a total of 27 and 9 citations were eligible for inclusion for Questions 1 and 2, respectively. In order to answer the two questions, odds ratios and 95% confidence intervals were calculated for all studies. The evidence was equivocal for a difference in risk of RDS in FGR compared with normally grown infants. Despite antenatal GC administration, there was evidence suggesting that the risk of RDS persists in FGR infants. The range of risk of RDS morbidity observed between studies is likely influenced by the definitions (RDS and FGR), gestational age, and small sample sizes of FGR infants evaluated. In addition, RDS morbidity may be related to the heterogeneous nature of FGR etiologies (including maternal, placental, and/or fetal factors). Further understanding of RDS morbidity and responsiveness to current treatments in FGR infants at a range of gestational ages, larger sample sizes, and stratification according to the specific etiology of FGR, may lead to improved respiratory outcomes at birth in this obstetric subpopulation.
Women at risk of preterm labor are commonly treated with antenatal glucocorticoids to reduce neon... more Women at risk of preterm labor are commonly treated with antenatal glucocorticoids to reduce neonatal complications, including respiratory distress syndrome. Despite the benefits of antenatal glucocorticoid for neonatal lung function, they are associated with negative cardiovascular outcomes. Among this population, there is a group of intrauterine growth-restricted fetuses in which substrate supply is reduced and these fetuses must undergo a range of cardiovascular adaptations to survive. Interestingly, the cardiovascular changes caused by antenatal glucocorticoid in normally grown fetuses are contrary to the cardiovascular adaptations that the intrauterine growth-restricted fetus must make to survive. Hence, the possibility exists that antenatal glucocorticoid in intrauterine growth-restricted infants may compromise cardiovascular development. This review first provides an overview of general antenatal glucocorticoid effects, before outlining the effects on cardiorespiratory development in normally grown fetuses, the cardiovascular adaptations that occur in the intrauterine growth-restricted fetus and finally integrating this with the very limited evidence for the effect of antenatal glucocorticoid in intrauterine growth-restricted infants.
The lungs of all air-breathing vertebrates contain a form of pulmonary surfactant that lines the ... more The lungs of all air-breathing vertebrates contain a form of pulmonary surfactant that lines the alveolar air-water interface where it modifies the interfacial surface tension. These pulmonary surfactants all consist of varying amounts of phospholipids (saturated and unsaturated) and cholesterol. The extent of variation between vertebrate groups and between species within a vertebrate group has been attributed to differences in factors such as phylogeny, body temperature, habitat, and lung structure. The influence of these factors on amphibian surfactant composition and function has been studied, but the reptiles, which comprise a polyphyletic group of vertebrates, have never been critically examined. The surfactant lipid composition from species belonging to the three groups of reptiles, the Archosauria (crocodiles), Lepidosauria (snakes and lizards), and Anapsida (turtles), has been determined. New data is presented in conjunction with already published data to create an evolutionary framework that concentrates particularly on the influence of phylogeny, body temperature, and lung structure on the composition of the surfactant lipids. Large amounts of pulmonary surfactant were found in all species of reptiles. All species lavaged at 23 degrees C (except C. atrox) demonstrated DSP/PL ratios of 23-33%. Animals with multicameral lungs exhibited an elevated CHOL/DSP ratio compared with species with unicameral lungs. In all groups, phosphatidylcholine (PC) was the dominant (60-80%) phospholipid. Phosphatidylserine and phosphatidylinositol (PS/PI) and sphingomyelin (S) represented the other phospholipids, while phosphatidylglycerol (PG), lysophosphatidylcholine (LPC), and phosphatidylethanolamine (PE) were occasionally observed. In two species of lizards (C. nuchalis and P. vitticeps), the saturated fatty acid, palmitic acid (16:0), was the dominant tail group on the phospholipids. Oleic acid (18:1) was the dominant monounsaturated fatty acid, whereas polyunsaturates comprised about a fifth of the total fatty acid profile. Short-term (4 h) changes in temperature did not affect the relative proportions of the fatty acids in either species. Comparison of the current data with previously published literature suggests that phylogeny and habitat do not significantly influence surfactant lipid composition, but body temperature and to a lesser extent lung structure are important determinants of reptilian surfactant lipid composition.
Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lining of the... more Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lining of the lung in response to ventilation, temperature changes and autonomic neurotransmitters. Type II cells were isolated from the heterothermic marsupial, Sminthopsis crassicaudata. The neurotransmitters, isoproterenol and carbamylcholine chloride significantly increased phosphatidylcholine secretion at 37 degrees C (basal: 14.2%, isoproterenol: 20.1%, carbamylcholine: 17.0%). Temperature reduced the rate of secretion from dunnart type II cells (e.g. basal: 14.2% at 37 degrees C; 7.2% at 18 degrees C). However, the change in secretory rate between 37 degrees C and 18 degrees C was less than expected if due to temperature alone (Q10= 1.4). The surfactant secretory pathway is therefore modulated by factors other than and in addition to, temperature. The response of dunnart type II cells to the agonists remained the same at both temperatures. Basal secretion was higher in dunnart type II cells (14.2% in 4 h) than has been reported in rat type II cells (1.9% in 3 h) and consequently, the agonist-stimulated increases in secretion from dunnart type II cells (41% above basal in 4 h) were much lower than observed for rat type II cells (200% above basal in 1.5 h).
American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2016
Intrauterine growth restriction induced by placental restriction (PR) in sheep leads to chronic h... more Intrauterine growth restriction induced by placental restriction (PR) in sheep leads to chronic hypoxemia and reduced surfactant maturation. The underlying molecular mechanism involves altered regulation of hypoxia signaling by increased prolyl hydroxylase domain (PHD) expression. Here, we evaluated the effect of intratracheal administration of the PHD inhibitor dimethyloxalylglycine (DMOG) on functional, molecular, and structural determinants of lung maturation in the control and PR sheep fetus. There was no effect of DMOG on fetal blood pressure or fetal breathing movements. DMOG reduced lung expression of genes regulating hypoxia signaling ( HIF-3α, ACE1), antioxidant defense ( CAT), lung liquid reabsorption ( SCNN1-A, ATP1-A1, AQP-1, AQP-5), and surfactant maturation ( SFTP-A, SFTP-B, SFTP-C, PCYT1A, LPCAT, ABCA3, LAMP3) in control fetuses. There were very few effects of DMOG on gene expression in the PR fetal lung (reduced lung expression of angiogenic factor ADM, water channel...
ABSTRACT Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lini... more ABSTRACT Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lining of the lung in response to ventilation, temperature changes and autonomic neurotransmitters. Type II cells were isolated from the heterothermic marsupial, Sminthopsis crassicaudata. The neurotransmitters, isoproterenol and carbamylcholine chloride significantly increased phosphatidylcholine secretion at 37 degrees C (basal: 14.2%, isoproterenol: 20.1%, carbamylcholine: 17.0%). Temperature reduced the rate of secretion from dunnart type II cells (e.g. basal: 14.2% at 37 degrees C; 7.2% at 18 degrees C). However, the change in secretory rate between 37 degrees C and 18 degrees C was less than expected if due to temperature alone (Q10= 1.4). The surfactant secretory pathway is therefore modulated by factors other than and in addition to, temperature. The response of dunnart type II cells to the agonists remained the same at both temperatures. Basal secretion was higher in dunnart type II cells (14.2% in 4 h) than has been reported in rat type II cells (1.9% in 3 h) and consequently, the agonist-stimulated increases in secretion from dunnart type II cells (41% above basal in 4 h) were much lower than observed for rat type II cells (200% above basal in 1.5 h).
Publisher Summary This chapter focuses on the adult pulmonary surfactant system and the effects o... more Publisher Summary This chapter focuses on the adult pulmonary surfactant system and the effects of aging process, respiratory diseases, and environmental factors on it. While very few studies have investigated the effect of aging on the pulmonary surfactant system, some evidence indicates that changes in surfactant may ameliorate the negative aging effects on lung architecture and function. Furthermore, aging has other effects, which could contribute to the effects of aging on surfactant composition, function, and regulation. Particularly, the autonomic nervous system; the immunological status of the lung such as numbers of alveolar macrophages, leukocytes and neutrophils, extent of phagocytosis, concentration of inflammatory mediators; and alveolo-capillary clearance all change with age and could impact on the composition and function of the surfactant system. The most common, serious surfactant-related disease is the acute respiratory distress syndrome (ARDS), in which pulmonary surfactant function is severely impaired, contributing to the high mortality rate of this disease. Major imbalances in total protein as well as surfactant-specific proteins occur during the progression of ARDS. Total protein is always markedly increased, due to the influx of plasma proteins, which exacerbates the poor surfactant function, as plasma proteins directly interfere with the surface tension lowering ability of the surfactant film. Impaired surfactant function, attributable to increased plasma protein leakage, has been demonstrated in animal models of asthma and in BAL fluid of asthmatic patients.
Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to ... more Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to negate the detrimental effects of oxidative stress on lung maturation. Antioxidants improve respiratory function in postnatal life and adulthood. However, the outcomes and biological mechanisms of antioxidant action in the fetal lung are unknown. Methods We investigated the effect of maternal daily vitamin C treatment (200 mg/kg, intravenously) for a month in late gestation (105–138 days gestation, term ~145 days) on molecular regulation of fetal lung maturation in sheep. Expression of genes and proteins regulating lung development was quantified in fetal lung tissue. The number of surfactant-producing cells was determined by immunohistochemistry. Results Maternal vitamin C treatment increased fetal lung gene expression of the antioxidant enzyme SOD-1, hypoxia signaling genes (HIF-2α, HIF-3α, ADM, and EGLN-3), genes regulating sodium movement (SCNN1-A, SCNN1-B, ATP1-A1, and ATP1-B1), sur...
Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to ... more Background In the fetus, the appropriate balance of prooxidants and antioxidants is essential to negate the detrimental effects of oxidative stress on lung maturation. Antioxidants improve respiratory function in postnatal life and adulthood. However, the outcomes and biological mechanisms of antioxidant action in the fetal lung are unknown. Methods We investigated the effect of maternal daily vitamin C treatment (200 mg/kg, intravenously) for a month in late gestation (105–138 days gestation, term ~145 days) on molecular regulation of fetal lung maturation in sheep. Expression of genes and proteins regulating lung development was quantified in fetal lung tissue. The number of surfactant-producing cells was determined by immunohistochemistry. Results Maternal vitamin C treatment increased fetal lung gene expression of the antioxidant enzyme SOD-1, hypoxia signaling genes (HIF-2α, HIF-3α, ADM, and EGLN-3), genes regulating sodium movement (SCNN1-A, SCNN1-B, ATP1-A1, and ATP1-B1), sur...
American Journal of Respiratory and Critical Care Medicine, 1994
We have tested the hypothesis that the composition of alveolar surfactant varies with pattern of ... more We have tested the hypothesis that the composition of alveolar surfactant varies with pattern of breathing and level of fitness. We examined three major components of surfactant, surfactant protein A (SP-A), disaturated phospholipids (DSP), and cholesterol (CHOL) in bronchoalveolar lavage (BAL) fluid from 12 healthy men before and after exercise. Fitness was assessed as work load/heart rate ([kpm.min-1]/[HR.HRmax-1]) achieved during cycling for 30 min at 90% theoretical maximal heart rate. Using a bronchoscope, four 20-ml vols of 0.15 M NaCl at 37 degrees C were instilled and then recovered from first a right upper and then a right lower lobe segmental bronchus. As we found no differences in the BAL from upper and lower lobes, the fluid was combined. We found a direct relationship between CHOL and DSP (rs = 0.84, p < 0.001), SP-A and CHOL (rs = 0.40, p < 0.025), and between SP-A and DSP (rs = 0.44, p < 0.025). The change in the ratios CHOL/DSP, SP-A/CHOL, and SP-A/DSP immediately after exercise was correlated with fitness (rs = -0.56, p < 0.025; rs = 0.75, p < 0.005; rs = 0.62, p < 0.025, respectively). We conclude that the composition of surfactant can change rapidly with exercise in a manner related to fitness, and we suggest that this is consistent with the existence of at least two pools of tissue surfactant of different composition supplying the alveolar compartment.
Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurologica... more Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurological and skeletal pathologies. Respiratory dysfunction is a secondary pathology contributing to mortality in MPS IIIA patients. Pulmonary surfactant is crucial to optimal lung function and has not been investigated in MPS IIIA. We measured heparan sulphate (HS), lipids and surfactant proteins (SP) in pulmonary tissue and bronchoalveolar lavage fluid (BALF), and surfactant activity in healthy and diseased mice (20 weeks of age). Heparan sulphate, ganglioside GM3 and bis(monoacylglycero)phosphate (BMP) were increased in MPS IIIA lung tissue. There was an increase in HS and a decrease in BMP and cholesteryl esters (CE) in MPS IIIA BALF. Phospholipid composition remained unchanged, but BALF total phospholipids were reduced (49.70%) in MPS IIIA. There was a reduction in SP-A, -C and -D mRNA, SP-D protein in tissue and SP-A, -C and -D protein in BALF of MPS IIIA mice. Captive bubble surfactometry...
Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth r... more Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth restriction that may influence respiratory outcome at birth. We investigated the effect of maternal chronic hypoxia for a month in late gestation on signalling pathways regulating fetal lung maturation and the transition to air-breathing at birth using isobaric hypoxic chambers without alterations to maternal food intake. Maternal chronic hypoxia in late gestation increases fetal lung expression of genes regulating hypoxia signalling, lung liquid reabsorption and surfactant maturation, which may be an adaptive response in preparation for the successful transition to air-breathing at birth. In contrast to other models of chronic fetal hypoxaemia, late gestation onset fetal hypoxaemia promotes molecular regulation of fetal lung maturation. This suggests a differential effect of timing and duration of fetal chronic hypoxaemia on fetal lung maturation, which supports the heterogeneity observe...
Administration of glucocorticoids (GCs) to women at risk of preterm delivery reduces the newborn&... more Administration of glucocorticoids (GCs) to women at risk of preterm delivery reduces the newborn's risk of respiratory distress syndrome (RDS) by 35% to 40%; however, not all infants respond to this treatment. Fetal growth restriction (FGR) increases the risk of prematurity, perinatal morbidity, and mortality. This review aims to synthesize current evidence reporting the difference in RDS risk between FGR and normally grown infants (Question 1) and whether antenatal GC administration reduces the risk of RDS morbidity in FGR infants (Question 2). Systematic searches were performed, and after screening, a total of 27 and 9 citations were eligible for inclusion for Questions 1 and 2, respectively. In order to answer the two questions, odds ratios and 95% confidence intervals were calculated for all studies. The evidence was equivocal for a difference in risk of RDS in FGR compared with normally grown infants. Despite antenatal GC administration, there was evidence suggesting that the risk of RDS persists in FGR infants. The range of risk of RDS morbidity observed between studies is likely influenced by the definitions (RDS and FGR), gestational age, and small sample sizes of FGR infants evaluated. In addition, RDS morbidity may be related to the heterogeneous nature of FGR etiologies (including maternal, placental, and/or fetal factors). Further understanding of RDS morbidity and responsiveness to current treatments in FGR infants at a range of gestational ages, larger sample sizes, and stratification according to the specific etiology of FGR, may lead to improved respiratory outcomes at birth in this obstetric subpopulation.
Women at risk of preterm labor are commonly treated with antenatal glucocorticoids to reduce neon... more Women at risk of preterm labor are commonly treated with antenatal glucocorticoids to reduce neonatal complications, including respiratory distress syndrome. Despite the benefits of antenatal glucocorticoid for neonatal lung function, they are associated with negative cardiovascular outcomes. Among this population, there is a group of intrauterine growth-restricted fetuses in which substrate supply is reduced and these fetuses must undergo a range of cardiovascular adaptations to survive. Interestingly, the cardiovascular changes caused by antenatal glucocorticoid in normally grown fetuses are contrary to the cardiovascular adaptations that the intrauterine growth-restricted fetus must make to survive. Hence, the possibility exists that antenatal glucocorticoid in intrauterine growth-restricted infants may compromise cardiovascular development. This review first provides an overview of general antenatal glucocorticoid effects, before outlining the effects on cardiorespiratory development in normally grown fetuses, the cardiovascular adaptations that occur in the intrauterine growth-restricted fetus and finally integrating this with the very limited evidence for the effect of antenatal glucocorticoid in intrauterine growth-restricted infants.
The lungs of all air-breathing vertebrates contain a form of pulmonary surfactant that lines the ... more The lungs of all air-breathing vertebrates contain a form of pulmonary surfactant that lines the alveolar air-water interface where it modifies the interfacial surface tension. These pulmonary surfactants all consist of varying amounts of phospholipids (saturated and unsaturated) and cholesterol. The extent of variation between vertebrate groups and between species within a vertebrate group has been attributed to differences in factors such as phylogeny, body temperature, habitat, and lung structure. The influence of these factors on amphibian surfactant composition and function has been studied, but the reptiles, which comprise a polyphyletic group of vertebrates, have never been critically examined. The surfactant lipid composition from species belonging to the three groups of reptiles, the Archosauria (crocodiles), Lepidosauria (snakes and lizards), and Anapsida (turtles), has been determined. New data is presented in conjunction with already published data to create an evolutionary framework that concentrates particularly on the influence of phylogeny, body temperature, and lung structure on the composition of the surfactant lipids. Large amounts of pulmonary surfactant were found in all species of reptiles. All species lavaged at 23 degrees C (except C. atrox) demonstrated DSP/PL ratios of 23-33%. Animals with multicameral lungs exhibited an elevated CHOL/DSP ratio compared with species with unicameral lungs. In all groups, phosphatidylcholine (PC) was the dominant (60-80%) phospholipid. Phosphatidylserine and phosphatidylinositol (PS/PI) and sphingomyelin (S) represented the other phospholipids, while phosphatidylglycerol (PG), lysophosphatidylcholine (LPC), and phosphatidylethanolamine (PE) were occasionally observed. In two species of lizards (C. nuchalis and P. vitticeps), the saturated fatty acid, palmitic acid (16:0), was the dominant tail group on the phospholipids. Oleic acid (18:1) was the dominant monounsaturated fatty acid, whereas polyunsaturates comprised about a fifth of the total fatty acid profile. Short-term (4 h) changes in temperature did not affect the relative proportions of the fatty acids in either species. Comparison of the current data with previously published literature suggests that phylogeny and habitat do not significantly influence surfactant lipid composition, but body temperature and to a lesser extent lung structure are important determinants of reptilian surfactant lipid composition.
Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lining of the... more Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lining of the lung in response to ventilation, temperature changes and autonomic neurotransmitters. Type II cells were isolated from the heterothermic marsupial, Sminthopsis crassicaudata. The neurotransmitters, isoproterenol and carbamylcholine chloride significantly increased phosphatidylcholine secretion at 37 degrees C (basal: 14.2%, isoproterenol: 20.1%, carbamylcholine: 17.0%). Temperature reduced the rate of secretion from dunnart type II cells (e.g. basal: 14.2% at 37 degrees C; 7.2% at 18 degrees C). However, the change in secretory rate between 37 degrees C and 18 degrees C was less than expected if due to temperature alone (Q10= 1.4). The surfactant secretory pathway is therefore modulated by factors other than and in addition to, temperature. The response of dunnart type II cells to the agonists remained the same at both temperatures. Basal secretion was higher in dunnart type II cells (14.2% in 4 h) than has been reported in rat type II cells (1.9% in 3 h) and consequently, the agonist-stimulated increases in secretion from dunnart type II cells (41% above basal in 4 h) were much lower than observed for rat type II cells (200% above basal in 1.5 h).
American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2016
Intrauterine growth restriction induced by placental restriction (PR) in sheep leads to chronic h... more Intrauterine growth restriction induced by placental restriction (PR) in sheep leads to chronic hypoxemia and reduced surfactant maturation. The underlying molecular mechanism involves altered regulation of hypoxia signaling by increased prolyl hydroxylase domain (PHD) expression. Here, we evaluated the effect of intratracheal administration of the PHD inhibitor dimethyloxalylglycine (DMOG) on functional, molecular, and structural determinants of lung maturation in the control and PR sheep fetus. There was no effect of DMOG on fetal blood pressure or fetal breathing movements. DMOG reduced lung expression of genes regulating hypoxia signaling ( HIF-3α, ACE1), antioxidant defense ( CAT), lung liquid reabsorption ( SCNN1-A, ATP1-A1, AQP-1, AQP-5), and surfactant maturation ( SFTP-A, SFTP-B, SFTP-C, PCYT1A, LPCAT, ABCA3, LAMP3) in control fetuses. There were very few effects of DMOG on gene expression in the PR fetal lung (reduced lung expression of angiogenic factor ADM, water channel...
ABSTRACT Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lini... more ABSTRACT Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lining of the lung in response to ventilation, temperature changes and autonomic neurotransmitters. Type II cells were isolated from the heterothermic marsupial, Sminthopsis crassicaudata. The neurotransmitters, isoproterenol and carbamylcholine chloride significantly increased phosphatidylcholine secretion at 37 degrees C (basal: 14.2%, isoproterenol: 20.1%, carbamylcholine: 17.0%). Temperature reduced the rate of secretion from dunnart type II cells (e.g. basal: 14.2% at 37 degrees C; 7.2% at 18 degrees C). However, the change in secretory rate between 37 degrees C and 18 degrees C was less than expected if due to temperature alone (Q10= 1.4). The surfactant secretory pathway is therefore modulated by factors other than and in addition to, temperature. The response of dunnart type II cells to the agonists remained the same at both temperatures. Basal secretion was higher in dunnart type II cells (14.2% in 4 h) than has been reported in rat type II cells (1.9% in 3 h) and consequently, the agonist-stimulated increases in secretion from dunnart type II cells (41% above basal in 4 h) were much lower than observed for rat type II cells (200% above basal in 1.5 h).
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