L-type Ca(2+) channels (LTCCs) are important for vascular smooth muscle cell (VSMC) contraction, ... more L-type Ca(2+) channels (LTCCs) are important for vascular smooth muscle cell (VSMC) contraction, as well as VSMC differentiation, as indicated by loss of LTCCs during VSMC dedifferentiation. However, it is not clear whether loss of LTCCs is a primary event underlying phenotypic modulation or whether loss of LTCCs has significance for vascular structure. We used small interference RNA (siRNA) transfection in vivo to investigate the role of LTCCs in VSMC phenotypic expression and structure of rat mesenteric arteries. siRNA reduced LTCC mRNA and protein expression in rat mesenteric arteries 3 days after siRNA transfection to 12.7 ± 0.7% and 47.3 ± 13%, respectively: this was associated with an increased resting intracellular Ca(2+) concentration ([Ca(2+)]i). Despite the high [Ca(2+)]i, the contractility was reduced (tension development to norepinephrine was 3.5 ± 0.2 N/m and 0.8 ± 0.2 N/m for sham-transfected and downregulated arteries respectively; P < 0.05). Expression of contractile phenotype marker genes was reduced in arteries downregulated for LTCCs. Phenotypic changes were associated with a 45% increase in number of VSMCs and a consequent increase of media thickness and media area. Ten days after siRNA transfection arterial structure was again normalized. The contractile responses of LTCC-siRNA transfected arteries were elevated in comparison with matched controls 10 days after transfection. The study provides strong evidence for causal relationships between LTCC expression and VSMC contractile phenotype, as well as novel data addressing the complex relationship between VSMC contractility, phenotype, and vascular structure. These findings are relevant for understanding diseases, associated with phenotype changes of VSMC and vascular remodeling, such as atherosclerosis and hypertension.
Voltage-gated sodium channels (VGSC) play a key role for initiating action potentials (AP) in exc... more Voltage-gated sodium channels (VGSC) play a key role for initiating action potentials (AP) in excitable cells. VGSC in human lymphatic vessels have not been investigated. In this study we describe the electrical activity and action potentials of small human lymphatic collecting vessels as well as mRNA expression and function of VGSC in small and large human lymphatic vessels. The VGSC blocker tetrodotoxin (TTX) inhibited spontaneous contractions in six of ten spontaneously active vessels whereas ranolazine, which has a narrower VGSC blocking profile, had no influence on spontaneous activity. Tetrodotoxin did not affect noradrenaline-induced contractions. The VGSC opener veratridine induced contractions in a concentration-dependent manner (0.1-30μM) eliciting a stable tonic contraction and membrane depolarisation to -18 ± 0.6 mV. Veratridine-induced depolarisations and contractions were ≈80% reversed by TTX, and were dependent on Ca(2+) influx via L-type calcium channels and the sodi...
L-type Ca(2+) channels (LTCCs) are important for vascular smooth muscle cell (VSMC) contraction, ... more L-type Ca(2+) channels (LTCCs) are important for vascular smooth muscle cell (VSMC) contraction, as well as VSMC differentiation, as indicated by loss of LTCCs during VSMC dedifferentiation. However, it is not clear whether loss of LTCCs is a primary event underlying phenotypic modulation or whether loss of LTCCs has significance for vascular structure. We used small interference RNA (siRNA) transfection in vivo to investigate the role of LTCCs in VSMC phenotypic expression and structure of rat mesenteric arteries. siRNA reduced LTCC mRNA and protein expression in rat mesenteric arteries 3 days after siRNA transfection to 12.7 ± 0.7% and 47.3 ± 13%, respectively: this was associated with an increased resting intracellular Ca(2+) concentration ([Ca(2+)]i). Despite the high [Ca(2+)]i, the contractility was reduced (tension development to norepinephrine was 3.5 ± 0.2 N/m and 0.8 ± 0.2 N/m for sham-transfected and downregulated arteries respectively; P < 0.05). Expression of contractile phenotype marker genes was reduced in arteries downregulated for LTCCs. Phenotypic changes were associated with a 45% increase in number of VSMCs and a consequent increase of media thickness and media area. Ten days after siRNA transfection arterial structure was again normalized. The contractile responses of LTCC-siRNA transfected arteries were elevated in comparison with matched controls 10 days after transfection. The study provides strong evidence for causal relationships between LTCC expression and VSMC contractile phenotype, as well as novel data addressing the complex relationship between VSMC contractility, phenotype, and vascular structure. These findings are relevant for understanding diseases, associated with phenotype changes of VSMC and vascular remodeling, such as atherosclerosis and hypertension.
Voltage-gated sodium channels (VGSC) play a key role for initiating action potentials (AP) in exc... more Voltage-gated sodium channels (VGSC) play a key role for initiating action potentials (AP) in excitable cells. VGSC in human lymphatic vessels have not been investigated. In this study we describe the electrical activity and action potentials of small human lymphatic collecting vessels as well as mRNA expression and function of VGSC in small and large human lymphatic vessels. The VGSC blocker tetrodotoxin (TTX) inhibited spontaneous contractions in six of ten spontaneously active vessels whereas ranolazine, which has a narrower VGSC blocking profile, had no influence on spontaneous activity. Tetrodotoxin did not affect noradrenaline-induced contractions. The VGSC opener veratridine induced contractions in a concentration-dependent manner (0.1-30μM) eliciting a stable tonic contraction and membrane depolarisation to -18 ± 0.6 mV. Veratridine-induced depolarisations and contractions were ≈80% reversed by TTX, and were dependent on Ca(2+) influx via L-type calcium channels and the sodi...
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Papers by Donna Boedtkjer