... Pituitary-Ovarian Function in Rats Exposed to Constant Light: A Chronological Study. ... Ovul... more ... Pituitary-Ovarian Function in Rats Exposed to Constant Light: A Chronological Study. ... Ovulation was still occurring in Group I; furthermore, the ovulatory surge of LH was being released at a time of day similar to that in animals exposed to a light-dark (LD) regimen. ...
Castration leads to a rapid increase in LH and FSH secretion, and exogenous gonadotropin-releasin... more Castration leads to a rapid increase in LH and FSH secretion, and exogenous gonadotropin-releasing hormone (GnRH) elicits supernormal secretion of LH and FSH after orchidectomy. Superimposition of adrenalectomy or pretreatment with cortisol prevents the acute castration-induced LH and FSH response seen within 24 h. The gonadotropin response to exogenous GnRH is not suppressed by adrenalectomy, indicating that adrenalectomy acts by preventing hypothalamic GnRH secretion and not by diminishing pituitary responsiveness to GnRH. Cortisol treatment severely reduces the response of LH to injected GnRH after castration, suggesting that cortisol suppression is at the pituitary level. Surprisingly, FSH secretory response to GnRH after orchidectomy is not suppressed by cortisol treatment, indicating a striking point of separate regulation of the two gonadotropins.
In order to examine pituitary gonadotropin secretion and responsiveness to GnRH after photic-indu... more In order to examine pituitary gonadotropin secretion and responsiveness to GnRH after photic-induced changes in reproductive condition, an in vitro pituitary perifusion system was established for male golden hamster tissue. Anterior pituitaries from adult males which had been maintained on 14 h light:10 h dark (long days) or 6 h light:18 h dark (short days) for 10 weeks were perifused using an Acusyst perifusion system. Perfusates from unstimulated tissue (basal secretion) and from tissue stimulated with hourly pulses of GnRH (25, 50, or 100 ng/ml) were assayed for LH and FSH by RIA. Tissue from short-day animals had lower basal LH secretion than tissue from long day animals, but there were no significant photoperiodic differences for GnRH-stimulated LH secretion. In contrast, there were no photoperiodic differences in basal FSH secretion, but tissue from short-day animals secreted more FSH than tissue from long-day animals when stimulated with GnRH. Bioactivity of a small number of perfusate samples was assessed using in vitro rat granulosa cell and mouse Leydig cell assays for FSH and LH, respectively, and did not show any photoperiodic differences in LH or FSH bioactivity for GnRH-stimulated tissue. These studies indicate that the pituitaries of gonadally regressed hamsters are capable in vitro of responding to GnRH with similar or greater levels of gonadotropin release compared to pituitaries from animals with functional gonads. Therefore, it appears that the lowered serum gonadotropin levels seen in vivo in gonadally regressed animals are not due to a reduction in intrinsic pituitary sensitivity to GnRH.
... See legend Fig. 6 for ng/ml; see legend Fig. 2. 1012 240 r 200 160 120 LYNN G. NEQUIN, JULIAN... more ... See legend Fig. 6 for ng/ml; see legend Fig. 2. 1012 240 r 200 160 120 LYNN G. NEQUIN, JULIAN ALVAREZ and NEENA B. SCHWARTZ 20a-OH-P OVA Cycl* Star Fig. 11. ... Tal-ley and Brigette Mann for their excellent technical assist-ance; Dr. John Marbarger. ...
To establish a sensitive and specific bioassay for the FSH-suppressing activity present in porcin... more To establish a sensitive and specific bioassay for the FSH-suppressing activity present in porcine follicular fluid (pFF), we examined the latency of pFF action when injected IV in the acutely ovariectomized (ovax) metestrous rat. By 2h post injection (5.5h after ovax), FSH was suppressed significantly in pFF vs. porcine serum-injected controls. LH was unaltered. In an experiment establishing a dose-response curve for pFF 4.5h after injection, 1.77 mg of pFF protein significantly suppressed FSH. The index of precision (-0.2188) and precision of slope (1.088) were well within acceptable limits for bioassays. We conclude that the ovax metestrous rat, injected 3.5h after surgery and sacrificed at 4.5 or 5.5h, is a sensitive and specific bioassay for folliculostatin.
Prepuberal patterns of pituitary luteinizing hormone (LH) con-tent in male and female rats were s... more Prepuberal patterns of pituitary luteinizing hormone (LH) con-tent in male and female rats were studied using the ovarian ascorbic acid-depletion bioassay technique. Pituitary LH content increases in both sexes until 26 days of age; however, the con-tent in the female is greater than in the male. After 26 days, pituitary LH content in the female reaches a plateau until the
Our previous work has suggested that glucocorticoid pretreatment suppresses the enhanced responsi... more Our previous work has suggested that glucocorticoid pretreatment suppresses the enhanced responsiveness to GnRH seen in serum LH 12 h after castration. By contrast, serum FSH continues to show the castration-induced hypersensitivity to GnRH. Our attempts to replicate this LH suppression in static pituitary culture in vitro were not successful. This suggested to us the possibility that corticoids in vivo might be preventing castration-induced increases in pituitary GnRH receptor levels. We tested this at 24 h post-castration and, in fact, corticoids did not suppress the increase in GnRH receptors. In addition to the aforementioned effects of corticoids, we have seen that cortisol reverses the castration-induced drop in pituitary FSH content. It does this for 7 days post-castration, even though it no longer has an effect in suppressing serum LH. Thus, our accumulated data reveal that glucocorticoids have a differential effect on LH and FSH synthesis and secretion. Further studies are ...
ABSTRACT The crucial participation of hormones in reproduction and fertility is the most complica... more ABSTRACT The crucial participation of hormones in reproduction and fertility is the most complicated story in endocrinology, because it involves several organ systems; gametes as well as hormones; two classes of receptors and intracellular signals; and a myriad of environmental factors such as seasonal signals and, of course, the nearby presence of a conspecific carrier of the opposite gamete type. As complicated as this system is in mammals, being quite different among major classes, it is even more complex when one deals with the vast number of nonmammalian vertebrate species. In a marvelous recent review, Rothchild discussed the evolution of placental mammals from other vertebrates. This chapter is limited to two mammals: the rat, which has been the species of choice for elucidating basic science, and the primate, which is obviously of major interest in dealing with clinical issues. The rat runs a 4- or 5-day estrous cycle, from the onset of follicular growth under the influence of follicle-stimulating hormone (FSH), to ovulation following an luteinizing hormone (LH) surge.
... Pituitary-Ovarian Function in Rats Exposed to Constant Light: A Chronological Study. ... Ovul... more ... Pituitary-Ovarian Function in Rats Exposed to Constant Light: A Chronological Study. ... Ovulation was still occurring in Group I; furthermore, the ovulatory surge of LH was being released at a time of day similar to that in animals exposed to a light-dark (LD) regimen. ...
Castration leads to a rapid increase in LH and FSH secretion, and exogenous gonadotropin-releasin... more Castration leads to a rapid increase in LH and FSH secretion, and exogenous gonadotropin-releasing hormone (GnRH) elicits supernormal secretion of LH and FSH after orchidectomy. Superimposition of adrenalectomy or pretreatment with cortisol prevents the acute castration-induced LH and FSH response seen within 24 h. The gonadotropin response to exogenous GnRH is not suppressed by adrenalectomy, indicating that adrenalectomy acts by preventing hypothalamic GnRH secretion and not by diminishing pituitary responsiveness to GnRH. Cortisol treatment severely reduces the response of LH to injected GnRH after castration, suggesting that cortisol suppression is at the pituitary level. Surprisingly, FSH secretory response to GnRH after orchidectomy is not suppressed by cortisol treatment, indicating a striking point of separate regulation of the two gonadotropins.
In order to examine pituitary gonadotropin secretion and responsiveness to GnRH after photic-indu... more In order to examine pituitary gonadotropin secretion and responsiveness to GnRH after photic-induced changes in reproductive condition, an in vitro pituitary perifusion system was established for male golden hamster tissue. Anterior pituitaries from adult males which had been maintained on 14 h light:10 h dark (long days) or 6 h light:18 h dark (short days) for 10 weeks were perifused using an Acusyst perifusion system. Perfusates from unstimulated tissue (basal secretion) and from tissue stimulated with hourly pulses of GnRH (25, 50, or 100 ng/ml) were assayed for LH and FSH by RIA. Tissue from short-day animals had lower basal LH secretion than tissue from long day animals, but there were no significant photoperiodic differences for GnRH-stimulated LH secretion. In contrast, there were no photoperiodic differences in basal FSH secretion, but tissue from short-day animals secreted more FSH than tissue from long-day animals when stimulated with GnRH. Bioactivity of a small number of perfusate samples was assessed using in vitro rat granulosa cell and mouse Leydig cell assays for FSH and LH, respectively, and did not show any photoperiodic differences in LH or FSH bioactivity for GnRH-stimulated tissue. These studies indicate that the pituitaries of gonadally regressed hamsters are capable in vitro of responding to GnRH with similar or greater levels of gonadotropin release compared to pituitaries from animals with functional gonads. Therefore, it appears that the lowered serum gonadotropin levels seen in vivo in gonadally regressed animals are not due to a reduction in intrinsic pituitary sensitivity to GnRH.
... See legend Fig. 6 for ng/ml; see legend Fig. 2. 1012 240 r 200 160 120 LYNN G. NEQUIN, JULIAN... more ... See legend Fig. 6 for ng/ml; see legend Fig. 2. 1012 240 r 200 160 120 LYNN G. NEQUIN, JULIAN ALVAREZ and NEENA B. SCHWARTZ 20a-OH-P OVA Cycl* Star Fig. 11. ... Tal-ley and Brigette Mann for their excellent technical assist-ance; Dr. John Marbarger. ...
To establish a sensitive and specific bioassay for the FSH-suppressing activity present in porcin... more To establish a sensitive and specific bioassay for the FSH-suppressing activity present in porcine follicular fluid (pFF), we examined the latency of pFF action when injected IV in the acutely ovariectomized (ovax) metestrous rat. By 2h post injection (5.5h after ovax), FSH was suppressed significantly in pFF vs. porcine serum-injected controls. LH was unaltered. In an experiment establishing a dose-response curve for pFF 4.5h after injection, 1.77 mg of pFF protein significantly suppressed FSH. The index of precision (-0.2188) and precision of slope (1.088) were well within acceptable limits for bioassays. We conclude that the ovax metestrous rat, injected 3.5h after surgery and sacrificed at 4.5 or 5.5h, is a sensitive and specific bioassay for folliculostatin.
Prepuberal patterns of pituitary luteinizing hormone (LH) con-tent in male and female rats were s... more Prepuberal patterns of pituitary luteinizing hormone (LH) con-tent in male and female rats were studied using the ovarian ascorbic acid-depletion bioassay technique. Pituitary LH content increases in both sexes until 26 days of age; however, the con-tent in the female is greater than in the male. After 26 days, pituitary LH content in the female reaches a plateau until the
Our previous work has suggested that glucocorticoid pretreatment suppresses the enhanced responsi... more Our previous work has suggested that glucocorticoid pretreatment suppresses the enhanced responsiveness to GnRH seen in serum LH 12 h after castration. By contrast, serum FSH continues to show the castration-induced hypersensitivity to GnRH. Our attempts to replicate this LH suppression in static pituitary culture in vitro were not successful. This suggested to us the possibility that corticoids in vivo might be preventing castration-induced increases in pituitary GnRH receptor levels. We tested this at 24 h post-castration and, in fact, corticoids did not suppress the increase in GnRH receptors. In addition to the aforementioned effects of corticoids, we have seen that cortisol reverses the castration-induced drop in pituitary FSH content. It does this for 7 days post-castration, even though it no longer has an effect in suppressing serum LH. Thus, our accumulated data reveal that glucocorticoids have a differential effect on LH and FSH synthesis and secretion. Further studies are ...
ABSTRACT The crucial participation of hormones in reproduction and fertility is the most complica... more ABSTRACT The crucial participation of hormones in reproduction and fertility is the most complicated story in endocrinology, because it involves several organ systems; gametes as well as hormones; two classes of receptors and intracellular signals; and a myriad of environmental factors such as seasonal signals and, of course, the nearby presence of a conspecific carrier of the opposite gamete type. As complicated as this system is in mammals, being quite different among major classes, it is even more complex when one deals with the vast number of nonmammalian vertebrate species. In a marvelous recent review, Rothchild discussed the evolution of placental mammals from other vertebrates. This chapter is limited to two mammals: the rat, which has been the species of choice for elucidating basic science, and the primate, which is obviously of major interest in dealing with clinical issues. The rat runs a 4- or 5-day estrous cycle, from the onset of follicular growth under the influence of follicle-stimulating hormone (FSH), to ovulation following an luteinizing hormone (LH) surge.
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Papers by Neena Schwartz