In Vitro Analysis of the Participation of Oxytocin and Vasopressin in the Gonadotropin Releasing Hormone-Induced Release of LH

Caffrey, M. H.; Nett, Terry M.; Kozlowski, Gerald P.

doi:10.3181/00379727-159-40367

Cited by 11 publications

(6 citation statements)

References 9 publications

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“…Although the ability of oxytocin and vasopressin to increase LH and FSH release in cultured pituitary cells has not been previously reported, a minor direct action of the neurohypophysial peptides on LH release has been observed in rat hemipituitaries (Caffrey, Nett & Kozlowski, 1978), in which oxytocin was more consistently active than vasopressin. At least two factors could be responsible for the inability to detect the direct gonadotrophin-releasing activities of neurohypophysial hormones in other earlier stud¬ ies.…”

Section: Discussionmentioning

confidence: 95%

Gonadotrophin-releasing activity of neurohypophysial hormones: I. Potential for modulation of pituitary hormone secretion in rats

Evans¹,

Robinson²,

Catt³

1989

Journal of Endocrinology

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Neurohypophysial hormones have been implicated in the control of anterior pituitary function, and oxytocin has been shown to stimulate gonadotrophin excretion and ovarian follicular development in certain species. To determine the role of neurohypophysial peptides in the control of gonadotrophin release, their actions on LH and FSH secretion were analysed in rats in vivo and in vitro. In adult female rats, administration of oxytocin during early pro-oestrus advanced the spontaneous LH surge and markedly increased peripheral LH levels at 15.00 h compared with control animals. In cultured pituitary cells from adult female rats, oxytocin and vasopressin elicited dose-related increases in LH and FSH release. Such responses were not affected by a potent gonadotrophin-releasing hormone (GnRH) antagonist that abolished GnRH agonist-induced release of LH and FSH. Oxytocin did not enhance GnRH agonist-stimulated gonadotrophin release to the same extent as it increased basal secretion, but at low concentrations of GnRH agonist the effects were additive. The gonadotrophin responses to oxytocin and vasopressin were inhibited by the specific neurohypophysial hormone antagonists, [d(CH2)5D-Ile2,Ile4,Arg8]vasopressin and [d(CH2)5Tyr (Me),Arg8]vasopressin. These results provide direct evidence that neurohypophysial hormones can stimulate gonadotrophin secretion through a receptor system distinct from the GnRH receptor. Such a mechanism could represent a complementary hypothalamic control system for long-term modulation of LH and FSH secretion by exerting a basal or tonic influence on gonadotrophin production.

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Section: Discussionmentioning

confidence: 95%

Gonadotrophin-releasing activity of neurohypophysial hormones: I. Potential for modulation of pituitary hormone secretion in rats

Evans¹,

Robinson²,

Catt³

1989

Journal of Endocrinology

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“…It increases the 697 urinary excretion of gonadotropins [21,29]; however, various investigators found no influence of oxytocin upon FSH and LH secretion in either in vitro or in vivo studies [1,5,[7][8][9]15]. It has been shown that intraventricular in jection of arginine vasopressin also increased LH release induced by LHRH [4], The administration of oxytocin on the morning of proestrus advanced the spontaneous LH surge and increased plasma LH and in dispersed anterior pituitary cells of adult female rats, oxytocin and vasopres sin increased LH and FSH release [30], In the present experiments with ovariectomized rats, there was no change of LH and FSH secretion after immunoneutralization of oxytocin or vasopressin. Therefore, in the con scious, ovariectomized rat, endogenous vasopressin and oxytocin appear to play little if any role in the control of gonadotropin secretion.…”

Section: Discussionmentioning

confidence: 99%

Actions of Endogenous Vasopressin and Oxytocin on Anterior Pituitary Hormone Secretion

Franci

Anselmo-Franci²,

Kozlowski³

et al. 1993

Neuroendocrinology

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To evaluate the significance of endogenous vasopressin and oxytocin in control of anterior pituitary hormone release, antiserum against vasopressin (AB-VP) or oxytocin (AB-OT) were microinjected into the third ventricle (3V) of conscious, ovariectomized rats to immunoneutralize endogenous VP or OT, respectively. Blood samples were collected just before and at different times after the microinjections. There were no differences in the plasma LH, FSH, PRL and TSH concentrations between control groups injected into the 3V with normal rabbit serum (NRS) and groups submitted to the intraventricular injection of AB-OT or AB-VP for 24 h after the injections. Plasma growth hormone (GH) declined significantly by 4 h after NRS injection, remained low at 6 h and had rebounded to nearly initial levels at 24 h. This pattern was not changed by microinjection of AB-VP, but plasma GH increased significantly compared to initial values in the period from 1 to 24 h after intraventricular microinjection of AB-OT. The intraventricular injection of AB-VP or AB-OT significantly decreased plasma ACTH; however, the effect of AB-VP was more prolonged and persisted for 6 rather than 4 h after injection. Thus, endogenous oxytocin may play a role in the control of basal GH release probably by stimulating somatostatin secretion and/or inhibiting GH-releasing hormone secretion or by both actions. On the other hand, both endogenous vasopressin and oxytocin play a physiologically significant stimulatory role in the control of basal ACTH release.

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“…injection it is possible that such large doses may have an appreciable effect on peripheral concentrations and hence raises the possibility of a direct inhibitory effect of AVP at the level of the pituitary gonadotrophs. This is unlikely, however, since in‐vitro studies have shown either no effect ( 36, 37) or a stimulatory effect ( 38, 39) of the peptide on LH release. Nevertheless, it has been demonstrated that peripheral administration of AVP inhibits the preovulatory LH surge in the rat ( 5), thus further work is required to clarify possible peripheral effects of AVP on LH release.…”

Section: Discussionmentioning

confidence: 99%

Stress‐Induced Suppression of Pulsatile Luteinising Hormone Release in the Female Rat: Role of Vasopressin

Cates

Forsling

O’Byrne

1999

J Neuroendocrinology

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Insulin-induced hypoglycaemic (IIH) stress evokes the release of arginine vasopressin (AVP) and suppresses luteinising hormone (LH) pulses in a number of species, a phenomenon augmented by the presence of oestradiol (E2). The aim of this study was to test the hypothesis that AVP not only disrupts pulsatile LH secretion in the female rat, but specifically mediates the effect of IIH stress on suppressing LH release. The role of E2 in augmenting the disruptive effect of AVP on LH secretion was also addressed. Rats were ovariectomized (OVX) and fitted with intracerebroventricular (i.c.v. ) and intravenous (i.v.) cannulae. For experiments requiring comparisons of neuroendocrine responses in the presence and absence of E2, animals were implanted subcutaneously with E2 or oil-filled capsules respectively. AVP (5 microg) administered via the i.c.v. cannula suppressed LH secretion by decreasing LH pulse amplitude without affecting LH pulse frequency, an effect that was blocked by central administration of an AVP antagonist (25 microg). This inhibitory response was evident only in E2-replaced OVX rats, thus suggesting a sensitizing influence of the gonadal steroid. In the AVP-deficient Brattleboro rats, IIH stress did not interrupt pulsatile LH secretion as demonstrated in Long Evans and Wistar controls. While these data might suggest a pivotal role for AVP in stress-induced suppression of LH release, central administration of an AVP antagonist did not prevent the interruption of LH pulses in response to IIH stress. Furthermore, it would appear that AVP is not primarily involved in hypoglycaemic stress-induced suppression of pulsatile LH secretion since central administration of very high doses of AVP resulted in a suppression of LH pulse amplitude and not frequency, while hypoglycaemic stress caused an interruption of LH pulses.

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In Vitro Analysis of the Participation of Oxytocin and Vasopressin in the Gonadotropin Releasing Hormone-Induced Release of LH

Cited by 11 publications

References 9 publications

Gonadotrophin-releasing activity of neurohypophysial hormones: I. Potential for modulation of pituitary hormone secretion in rats

Gonadotrophin-releasing activity of neurohypophysial hormones: I. Potential for modulation of pituitary hormone secretion in rats

Actions of Endogenous Vasopressin and Oxytocin on Anterior Pituitary Hormone Secretion

Stress‐Induced Suppression of Pulsatile Luteinising Hormone Release in the Female Rat: Role of Vasopressin

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