Differential effects of melatonin on the stimulated release of LH from dispersed pituitary cells of the prepubertal female rat

Symons, A. M.; Arendt, J; Pryde, S. J.

doi:10.1677/joe.0.1070107

Cited by 10 publications

(5 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The inhibitory effect of melatonin on GnRHinduced LH release from the anterior pitu itary appears to be lost as the rat matures [ 16,17], In addition, in vivo studies showed that melatonin was able to suppress LH and FSH secretion from hamster pituitaries [18] and melatonin treatment was found to duplicate the effect of short photoperiod on occupancy and kinetic parameters of androgen receptors not only in the hypothalamus but also in the pituitary [19].…”

Section: Introductionmentioning

confidence: 99%

2-[<sup>125</sup>I]Iodomelatonin Binding Sites in the Testis and Ovary: Putative Melatonin Receptors in the Gonads

Ayre

Pang

1994

Neurosignals

View full text Add to dashboard Cite

Through the synthesis and secretion of the hormone, melatonin, the pineal has been assigned the role of synchronizing a reproductive response to appropriate environmental conditions. Theoretical melatonin target sites may occur at several levels of the hypothalamic-pituitary-gonadal hierarchy, including a direct action on the gonads. The availability of a biologically active radioligand, 2-[¹²⁵I]iodomelatonin, has provided the opportunity to examine the possible direct melatonin action on the gonads. 2-[¹²⁵I]Iodomelatonin binding sites were identified in the testes and ovaries of chickens, ducks and quail but were not measurable in mammalian gonads, with the exception of tree shrew testes. The avian gonadal 2-[¹²⁵I]iodomelatonin binding sites were stable, saturable, reversible, specific and of high affinity. 2-[¹²⁵I]Iodomelatonin appeared to label a single class of binding sites as evidenced by the linearity of Rosenthal analysis of the specific binding data, the Hill coefficients close to unity and the monophasic competition curves. The high affinity on the gonadal 2-[¹²⁵I]iodo-melatonin binding sites, characterized by apparent equilibrium dissociation constants in the low picomolar range, was in accordance with circulating levels of melatonin suggesting that they may be physiologically relevant. Autoradiography indicated that these 2-[¹²⁵I]iodomelatonin binding sites were widely distributed throughout the testes but localized in ovarian follicles in the birds studied. Specific inhibition of testicular 2-[¹²⁵I]iodomelatonin binding by a guanine nucleotide analog has provided evidence that the 2-[^l25I]iodomelatonin binding sites in chicken testes may be coupled to a guanine nucleotide binding protein-effector system, thus promoting the idea that testicular 2-[¹²⁵I]iodomelatonin binding sites may mediate a cascade of intracellular events. Although no circadian rhythm in the density or affinity of 2-[¹²⁵I]iodomelatonin binding in chicken ovaries was found, there was a decrease in 2-[^I25I]iodomelatonin binding affinity at middark in chicken testes with no change in the number of testicular 2-[¹²⁵I]iodomelatonin binding sites. The present evidence is in line with the hypothesis of a direct melatonin action on the gonads and further investigations on the above problem will be rewarding.

show abstract

Section: Introductionmentioning

confidence: 99%

2-[<sup>125</sup>I]Iodomelatonin Binding Sites in the Testis and Ovary: Putative Melatonin Receptors in the Gonads

Ayre

Pang

1994

Neurosignals

View full text Add to dashboard Cite

show abstract

“…Previous studies have shown that melatonin is in volved in the neuroendocrine regulation of reproduction in various mammalian species of both seasonal and nonseasonal breeders [1], In immature rats, for example, melatonin administration delays the sexual maturation [2,3], inhibits pregnant mare's serum-induced luteinizing hormone (LH) release and ovulation [4], and suppresses the pituitary responsiveness to LH-releasing hormone (LHRH) [5]. In the adult female rat, injection of a large dose of melatonin on the afternoon of proestrus inhibits the preovulatory LH surge and eliminates the expected ovulation [6], and the nocturnal administration of mela …”

Section: Introductionmentioning

confidence: 99%

Effects of Pinealectomy and Melatonin on the Timing of the Proestrous Luteinizing Hormone Surge in the Rat

Chiba

Akema²,

Toyoda³

1994

Neuroendocrinology

View full text Add to dashboard Cite

Effects of pinealectomy and melatonin replacement on the timing of the preovulatory luteinizing hormone (LH) surge were examined in female rats housed under a light-dark cycle (lights on 06:30–18:30 h). Animals were pinealectomized or sham-operated 21-28 days before bleeding. They were sequentially bled in the afternoon of proestrus through the indwelling cardiac cannula without anesthesia. Proestrous LH surges were observed in all pinealectomized rats, but the onset times of the LH surge in these animals showed a significantly greater variance than those in sham-operated controls. A single melatonin injection at 18:00 or 21:00, shortly before or after the light-dark transition, on the day before proestrus (diestrus II) reduced the variance in the LH surge onset in pinealectomized rats in a dose-dependent manner. In contrast, melatonin injected at 14:00 or 23:00 on diestrus II or at 04:00 on proestrus was ineffective. These results showed that the pineal gland is involved in controlling the timing of the proestrous LH surge in the rat. The pineal signal may be transmitted by melatonin, a major product of the gland.

show abstract

“…Martin et al (1982) found that the addition of I O -~ M melatonin to a culture medium would suppress the response of rat gonadotrophs to Gn-RH and that the degree of inhibition ranged from complete to partial depending on the concentration of Gn-R H used. Using a perfusion system, Symons et al (1985) found that the secretion of LH induced by both Gn-RH and by calcium ionophore was significantly inhibited in the presence of melatonin (2.5 x 10-l' M).…”

Section: Discussionmentioning

confidence: 99%

“…They probably act primarily in the hypothalamus to regulate the production of releasing or inhibiting hormones (Karasek 1985). Melatonin is also capable of reducing the response of gonadotrophs in cell culture to gonadotrophin-releasing hormone (Gn-RH) (Symons et al 1985), so there is also the possibility of a direct action by pineal hormones on the pituitary.…”

mentioning

confidence: 99%

Melatonin reduces the production and secretion of prolactin and growth hormone from rat pituitary cells in culture

Griffiths

Bjøro²,

Gautvik

et al. 1987

Acta Physiologica Scandinavica

View full text Add to dashboard Cite

A culture of clonal tumour cells from rat pituitary gland that secrete both prolactin and growth hormone were used to investigate whether the pineal hormone melatonin can act directly on the pituitary gland to control prolactin production. Melatonin inhibition of prolactin and growth hormone production was significant but mild. Concentrations of between 10(-8) M and 10(-6) M reduced both prolactin and growth hormone production and prolactin secretion by 10-50%. 17 beta-oestradiol (OE) and thyrotrophin-releasing hormone (TRH) stimulated prolactin production but had no significant effect on growth hormone production. Melatonin reduced the effects of both of these compounds. Both TRH and vasoactive intestinal peptide (VIP) stimulated secretion of prolactin, and TRH also of growth hormone. Melatonin reduced these effects significantly. TRH and VIP increased cAMP production two- and 12-fold, respectively. Melatonin had no effect on basal or stimulated cAMP production. The melatonin-induced changes in prolactin and growth hormone production and secretion seen here do not approach the magnitude of the fluctuations seen in plasma in vivo. It is concluded that while melatonin does have a direct effect on the lactotroph in the regulation of prolactin production, its main physiological target must be elsewhere.

show abstract

Differential effects of melatonin on the stimulated release of LH from dispersed pituitary cells of the prepubertal female rat

Cited by 10 publications

References 20 publications

2-[<sup>125</sup>I]Iodomelatonin Binding Sites in the Testis and Ovary: Putative Melatonin Receptors in the Gonads

2-[<sup>125</sup>I]Iodomelatonin Binding Sites in the Testis and Ovary: Putative Melatonin Receptors in the Gonads

Effects of Pinealectomy and Melatonin on the Timing of the Proestrous Luteinizing Hormone Surge in the Rat

Melatonin reduces the production and secretion of prolactin and growth hormone from rat pituitary cells in culture

Contact Info

Product

Resources

About