Stimulation of pituitary LH and FSH secretion after immunoneutralization of endogenous substance P in the cycling rat]

In the cycling female Rat, administration of substance P antisera performed at noon on the proestrous day provokes a significant increase in LH and FSH serum level, right before or after the preovulatory surges, but had no effect on its occurrence or magnitude. These results suggest that substance P has a normal physiological inhibitory role in gonadotropin regulation.     

Gonadotrophin-releasing activity of histones H2A and H2B

We report that histones H2A and H2B possess gonadotrophin-releasing activity in vitro and assess the signal transduction pathways involved in these effects. Perifused and incubated rat anterior pituitary (AP) cells were used, and luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured by RIA. Perifusion of cells with histone H2A (30 μM) or histone H2B (30 μM), markedly stimulated LH release but failed to elicit any FSH response. Cells incubated with 6 or 30 μM histone H2A showed a dose- and time-dependent stimulatory effect on both LH and FSH release which was blocked by 1 μM peptide MB35, an 86–120 amino acid fragment of histone H2A. Incubation of pituitary cells with gonadotrophin-releasing hormone (GnRH) and histones H2A or H2B showed a stimulatory effect on LH and FSH release which was similar to the sum of the separate effects. Trifluoperazine, as well as ethylene glycol bis(b-aminoethyl ether) N,N,N′,N′-tetraacetic acid (EGTA), alone or in the presence of the calcium ionophore A23187, significantly reduced the response of AP cells to histones. Various cyclic adenosine monophosphate (cAMP) enhancers had no effect on histone-stimulated release of gonadotrophins in incubated AP cells. Our results confirm previous evidence that histones may act as hypophysiotrophic signals. Calcium- and diacylglycerol-associated pathways, but not cAMP, appear to participate in these effects. Received 11 August 1997; received after revision 20 January 1998; accepted 26 January 1998     

Similarity between the effects of suprachiasmatic nuclei lesions and of pinealectomy on gonadotropin release in ovariectomized,sulpiride-treated and melatonin-replaced rats

The aim of this study was to compare the effects of pineal indole treatments on LH and FSH release in pinealectomized and suprachiasmatic lesioned and ovariectomized rats rendered hyperprolactinemic by acute sulpiride treatment. pinealectomy or suprachiasmatic nuclei lesions in female rats both decreased plasma LH and FHS at 10, but not at 20 d after surgery, whereas the daily afternoon administration of melatonin effectively restored levels of both gonadotropins to control values. In ovariectomized rats, pinealectomy or suprachiasmatic nuclei lesions were ineffective in counteracting the high plasma levels of LH and FSH. However, sulpiride treatment in both pinealectomized and suprachiasmatic nuclei lesioned and castrated female rats significantly decreased the levels of LH and FSH, an effect which was counteracted by daily afternoon melatonin administration. Other pineal indoles tested, i.e., 5-hydroxy- and 5-methoxytryptophol, were ineffective in regulating gonadotropin levels. The results suggest that the pineal gland, through its hormone melatonin, can modulate gonadotropin secretion by acting on a dopamine mechanism independent of hypothalamic suprachiasmatic areas.     

Effects of prolactin (PRL) on gonadotropin release in mice with congenital PRL deficiency

Summary In prolactin (PRL)-deficient male dwarf mice, treatment with PRL stimulates the release of FSH without affecting plasma LH levels. We now report that this effect of PRL is not mediated by the testes and that PRL does not modify FSH or LH release in female dwarf mice.This work was supported by the National Institute of Child Health and Human Development through a grand HD12642 and RIA Core of grant HD10202. We thank NIAMDD and Drs G.D. Niswender and L.E. Reichert, Jr, for reagents used in radioimmunoassays.     

The effect of gonadotrophins on the steroidogenesis, in the ovary and testis of gonadotrophin-deprived fresh water teleost, Cyprinus carpio.

Studies have been made on the effect of LH, FSH, and LH+FSH on the gonadal steroidogenesis in gonadotrophin-deprived common carp. LH alone and in combination with FSH was more effective than FSH in stimulation of steroidogenesis.     

Effects of progesterone implants in the mesencephalon of ovariectomized rats on LH and FSH release triggered by exogenous gonadal steroids

Unilateral implantation of crystalline progesterone into the caudal mesencephalic reticular formation (MRF) of chronically ovariectomized adult rats prevents the triggering effect of exogenous gonadal steroids on LH release and does not affect the release of FSH in the same animal.     

The effect of gonadotrophins on the steroidogenesis,in the ovary and testis of gonadotrophin-deprived fresh water teleost,Cyprinus carpio

Summary Studies have been made on the effect of LH, FSH, and LH+FSH on the gonadal steroidogenesis in gonadotrophin-deprived common carp. LH alone and in combination with FSH was more effective than FSH in stimulation of steroidogenesis.Acknowledgment. K.K. is thankful to University Grants Commission, Govt. of India, for a fellowship. Tranks are due to Dr R.W. Bates, NIH Bethesda, for the supply of bovine LH and FSH, and to ICI England for the supply of methallibure.     

Clomiphene citrate can mimic the augmentative (positive) but not the depressing (negative) effect of estradiol on the LHRH-stimulated release of LH and FSH by the pituitary gland of the long-term ovariectomized rat

Summary In the long-term ovariectomized rat, both estradiol benzoate (EB) and clomiphene citrate enhance the release of LH induced by luteinizing hormone-releasing hormone (LHRH). EB also enhances the release of FSH. In rats pretreated with LHRH, EB strongly depresses the LHRH-induced LH/FSH release, but clomiphene enhances this release, regardless of the presence of EB.     

Clomiphene citrate can mimic the augmentative (positive) but not the depressing (negative) effect of estradiol on the LHRH-stimulated release of LH and FSH by the pituitary gland of the long-term ovariectomized rat

In the long-term ovariectomized rat, both estradiol benzoate (EB) and clomiphene citrate enhance the release of LH induced by luteinizing hormone-releasing hormone (LHRH). EB also enhances the release of FSH. In rats pretreated with LHRH, EB strongly depresses the LHRH-induced LH/FSH release, but clomiphene enhances this release, regardless of the presence of EB.     

Hyperprolactinemia and estrogen-induced rhythms in LH and prolactin release in the ovariectomized rat

Short-term (9 days) hyperprolactinemia induced by pituitary grafts reduced basal plasma LH levels in ovariectomized rats whereas long-term (31 days) grafts increased basal LH levels. Although long-term grafts inhibited estradiol-induced prolactin surges, hyperprolactinemia had no effect on the LH surge. It is concluded that the estrogen-treated ovariectomized rat is not suitable for studying the effects of hyperprolactinemia on LH release.     

Hyperprolactinemia and estrogen-induced rhythms in LH and prolactin release in the ovariectomized rat

Summary Short-term (9 days) hyperprolactinemia induced by pituitary grafts reduced basal plasma LH levels in ovariectomized rats whereas long-term (31 days) grafts increased basal LH levels. Although long-term grafts inhibited estradiol-induced prolactin surges, hyperprolactinemia had no effect on the LH surge. It is concluded that the estrogen-treated ovariectomized rat is not suitable for studying the effects of hyperprolactinemia on LH release.     

Neuroendocrine effects of a non-steroidal compound of testicular origin

Summary The effects of the compound (+)-1,4-diphenylbutane-2,3-diol (DPB, synthetized in the testes) on gonadotropin secretion have been studied in castrated male rats. DPB, when injected subcutaneously, does not modify serum levels of LH and FSH. On the contrary, the local implantation of DPB in the median eminence of the hypothalamus results in a significant elevation of serum FSH. It is suggested that DPB may play a physiological role in the control of FSH release.This work has been supported by grants of the Ford Foundation, New York, and of the CNR, Biology of Reproduction Program, Rome. Kits for LH and FSH radioimmunoassay have been kindly provided by the Rat Pituitary Hormone Distribution Program of the National Institutes of Arthritis, Metabolism and Digestive Diseases of the National Institutes of Health. Diphenylbutane was a kind gift of Dr R. Neher of the Ciba-Geigy Laboratories, Basel, to Dr Iturriza. Thanks are also due to Mrs Paola Assi Brunone for her skilful technical assistance.     

Enhancement of serum FSH levels after pinealectomy

The effect of pinealectomy on the circadian periodicity in serum gonadotropins was investigated in adult male rats. Pinealectomy resulted in an elevation of the serum FSH concentration 7 days after the operation. A 4-fold increase in serum FSH over 24 h with no concommitant increase in serum LH following pinealectomy suggests that the control of FSH secretion could be mediated via the pineal gland.     

Enhancement of serum FSH levels after pinealectomy

Summary The effect of pinealectomy on the circadian periodicity in serum gonadotropins was investigated in adult male rats. Pinealectomy resulted in an elevation of the serum FSH concentration 7 days after the operation. A 4-fold increase in serum FSH over 24 h with no concommitant increase in serum LH following pinealectomy suggests that the control of FSH secretion could be mediated via the pineal gland.     

Peptide-stimulated release of prolactin from the fowl anterior pituitary gland

Summary Anterior pituitary glands from broiler fowl were preincubated for 24 h in either medium 199 only or medium containing estradiol 17, following which they were incubated in medium containing thyrotrophin releasing hormone (TRH), vasoactive intestinal polypeptide (VIP) or substance P (SP), alone or with the dopamine agonist, apomorphine. Estradiol priming stimulated release of prolactin and enhanced apomorphine-inhibition of prolactin release. TRH stimulated prolactin release, an effect reversed by apomorphine, and priming with estradiol potentiated both effects. VIP stimulated prolactin to a lesser degree and again this was inhibited by apomorphine and potentiated by estradiol. SP had little effect on the nonsteroid-primed pituitary, but stimulated release of prolactin after estradiol treatment, though less effectively than TRH or VIP.     

Modifications of ovarian follicle reactivity to LH in rats treated with FSH at the beginning of the estrous cycle]

LH perfusion was performed on proestrus under pentobarbital anaesthesia in 4-days cyclic female Rats treated or not treated with FSH at the onset of estrous cycle. The number of follicles capable of undergoing luteinization was shown to be dependent upon the amount of LH available.     

Gonadostatin and gonadocrinin, polypeptides of ovarian origin with hypophysiotropic activity]

Crude acetic acid extract of Rat ovaries pretreated with pregnant mare serum (PMSG) contains native peptides with two types of separable biological activities: one, molecular weight greater than 10,000 dalton inhibits the secretion of both LH and FSH as stimulated by luteinizing hormone releasing factor (LRF) in a pituitary monolayer culture system and is referred to as gonadostatin; the other, less than 3,500 dalton, stimulates the secretion of gonadotropins and is designated as gonadocrinin. The biological activities of ovarian gonadocrinin can be competitively inhibited by an LRF-analog-antagonist, D-Phe2, D-Trp6-LRF. These ovarian peptides may participate in physiological control of pituitary LH/FSH secretion.     

Plurihormonality in the secretory granules of the normal human pituitary. An immunoelectron microscopic study

Normal human autopsy anterior pituitary tissue from 5 cases was embedded in LR White resin and immunolabelled using silver-enhanced 5-nm protein A gold probes. Follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), adrenocorticotrophic hormone (ACTH), growth hormone (GH) and prolactin (PRL) were immunolocalised to the level of secretory granule. A two-sided double-labelling method was used to cross-react two hormones at a time with respect to their corresponding antibodies. All possible combinations of the six pituitary hormones were tested. Plurihormonal granules were found that contained LH + FSH, LH + TSH, and FSH + TSH. Each hormone was also found in monohormonal granules. Granule diameter was significantly larger in the pluri as opposed to monohormonal granules.     

Plurihormonality in the secretory granules of the normal human pituitary. An immunoelectron microscopic study

Summary Normal human autopsy anterior pituitary tissue from 5 cases was embedded in LR White resin and immunolabelled using silver-enhanced 5-nm protein A gold probes. Follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), adrenocorticotrophic hormone (ACTH), growth hormone (GH) and prolactin (PRL) were immunolocalised to the level of secretory granule.A two-sided double-labelling method was used to cross-react two hormones at a time with respect to their corresponding antibodies. All possible combinations of the six pituitary hormones were tested. Plurihormonal granules were found that contained LH+FSH, LH+TSH, and FSH+TSH. Each hormone was also found in monohormonal granules. Granule diameter was significantly larger in the pluri as opposed to monohormonal granules.     

Stimulation of the secretion of LH and FSH and increase in testicular weight at birth in rats]

The evolutions of serum LH and FSH concentrations and of testicular weight have been measured in the newborn Rat before, during and up to 24 hrs. after birth. A sudden and transient increase of LH and FSH is observed at birth. The testicular weight rises rapidly between 2 and 4 hrs.