Effects of induced hypoprolactinaemia in the ram : plasma gonadotrophin levels, LH and FSH receptors and histology of the testis

Barenton, Bruno; Reviers, M.T. Hochereau de; Perreau, C.; Poirier, J. C.

doi:10.1051/rnd:19820504

Cited by 15 publications

(13 citation statements)

References 16 publications

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“…These results are in agreement with studies in which CB-154 was administered to ewes during the oestrous cycle (Niswender, 1974) or in seasonal anoestrus (McNeilly and Land, 1979;Land et al, 1980) and to rams (Barenton et al, 1982;Ravault et al, 1982;Regisford and Katz, 1993). In sheep, dopamine controls prolactin secretion via specific D1 receptors located in the ventromedial hypothalamus (Curlewis et al, 1995;Colthorpe and Curlewis, 1996) and D2 receptors on the pituitary lactotrophs (Curlewis et al, 1993).…”

Section: Discussionsupporting

confidence: 81%

“…Studies in sheep showed no effects of the agonist on FSH plasma concentrations when given to seasonal anoestrous ewes to suppress prolactin (Land et al, 1980) and Katz, 1993). The results from the present study are in contrast with observations in lactating women (Seki et al, 1974) and in Ile de France rams in the summer (Barenton et al, 1982) and winter (Ravault et al, 1982) in which bromocriptine caused an increase in FSH plasma concentrations. Increased plasma FSH concentrations might be expected as a result of the inhibitory effects of the agonist on LH pulsatile secretion, which would decrease oestradiol secretion leading to augmented plasma FSH concentrations.…”

Section: Discussioncontrasting

confidence: 57%

“…In conclusion, the effects of bromocriptine on gonadotrophin and prolactin secretion and on the follicular dynamics during the follicular phase of the sheep oestrous cycle indicate that prolactin may influence the viability of gonadotrophin-responsive follicles shortly after luteolysis. et al, 1982;Tsai-Morris et al, 1983) secretion of oestrogens. Administration of bromocriptine to pregnant gilts to suppress prolactin secretion resulted in an increase in the secretion of oestradiol (Szafranska and Ziecik, 1990).…”

mentioning

confidence: 99%

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Effects of bromocriptine administration during the follicular phase of the oestrous cycle on prolactin and gonadotrophin secretion and follicular dynamics in merino monovular ewes

Picazo¹,

Bulnes²,

Brunet³

et al. 2000

Reproduction

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Section: Discussionsupporting

confidence: 81%

Section: Discussioncontrasting

confidence: 57%

mentioning

confidence: 99%

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Effects of bromocriptine administration during the follicular phase of the oestrous cycle on prolactin and gonadotrophin secretion and follicular dynamics in merino monovular ewes

Picazo¹,

Bulnes²,

Brunet³

et al. 2000

Reproduction

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“…Suppression of PRL secretion can result in hyperplasia of Leydig cells, but the cells tend to be small and unable to sustain intratesticular testosterone concentration (Barenton & Pelletier 1980, Barenton et al 1982. These events occur without changes in LH release or the number of LH receptors per Leydig cell.…”

Section: Discussionmentioning

confidence: 99%

“…Our first aim was to determine whether PRL promotes the expression of LH receptors, as it does in several rodent species (Bartke 2004), thereby enhancing the response of Leydig cells to LH stimulation when the testes are regressed and (or) beginning to redevelop. The role of endogenous PRL in modulating LH receptors has been evaluated only when the testes are well developed (Barenton et al 1982, Regisford & Katz 1994 and not during the crucial period of testicular activation. Our second aim was to determine if PRL attenuates the amplitude of LH pulses, thus providing a negative control of testosterone secretion.…”

Section: Introductionmentioning

confidence: 99%

Prolactin regulation of testosterone secretion and testes growth in DLS rams at the onset of seasonal testicular recrudescence

Sanford

Baker²

2010

Reproduction

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Our objective was to test the hypothesis that prolactin (PRL) acts at both the pituitary and testis levels to regulate testosterone secretion in the adult ram. The focus was on the mid-regression to mid-redevelopment stages of a photoperiod-condensed 'seasonal' testicular cycle. DLS rams (six per group) were given daily s.c. injections of bromocriptine (4 mg) or vehicle during the entire period. Serum PRL concentration in control rams peaked at 103.4G22.1 ng/ml in late regression and then steadily declined (P!0.01) to 19.5G4.3 ng/ml, whereas PRL in treated rams was always %4.0 ng/ml. Suppression of PRL tended (P!0.10) to increase the amplitude of natural LH pulses (transition stages) or reduce the number of LH receptors in the testis (regressed stage), although neither change disturbed testosterone levels in peripheral blood. These subtle changes were accompanied by significant (P!0.05) alterations in the capability of the pituitary to release LH (85% more) and of the testes to secrete testosterone (20% less). These effects of PRL were unmasked when rams were given highly stimulative i.v. injections of GNRH (single 3 mg dose) and NIH-oLH-S24 (three 5 mg doses given 20 min apart) respectively. PRL insufficiency also appeared to slow down the 'seasonal' rise in FSH secretion and slightly delayed (2 weeks) the times when the testes began to grow and were first significantly (P!0.05) enlarged from the regressed state. We conclude that PRL is an important part of the intricate regulation of the pituitary-gonadal system in moderately seasonal DLS rams.

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Prolactin in the Male: 25 Years Later

Bartke

2004

Journal of Andrology

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In an article published 25 years ago in the first volume of the Journal of Andrology (Bartke et al, 1980), we reported evidence of involvement of prolactin (PRL) in the control of testicular growth in the golden hamster. In this seasonally breeding species, testes undergo regression in the fall and recover their size and activity the following spring. PRL-secreting transplants of anterior pituitaries augmented the stimulatory effect of treatment with human chorionic gonadotropin on the recrudescence of the regressed testes, while treatment with an inhibitor of PRL release, bromocriptine, delayed recrudescence of the testes and the seminal vesicles induced by exposure to long photoperiods. Role of PRL in the Control of Seasonal Breeding in the Male HamsterStudies conducted in our laboratory following the abovereferenced report of the effects of bromocriptine (Bartke et al, 1980) reaffirmed the role of photoperiod-induced alterations in plasma PRL levels in the control of seasonal transitions between periods of full testicular activity and testicular quiescence in the golden hamster and identified a number of mechanisms involved in the actions of PRL. In the male golden hamster, PRL acts at multiple levels of the hypothalamic-pituitary-testicular axis. In the hypothalamus, it modifies the turnover of neurotransmitters involved in the control of the pituitary (Steger et al, , 1984. In the pituitary, it influences the number of androgen receptors (Prins et al, 1988). Actions of PRL on the hypothalamic-adenohypophyseal system result in the stimulation of follicle-stimulating hormone (FSH) synthesis and release Steger et al, 1983;Carrillo et al, 1984) and reduction of the sensitivity of gonadotropin release to negative testosterone feedback Our studies of the role of PRL in seasonal breeders were supported by NICHD.Correspondence to: Dr Andrzej Bartke, Departments of Physiology and Internal Medicine, Southern Illinois University School of Medicine, 801 N Rutledge, Springfield, IL 62794-9628 (e-mail: abartke@siumed.edu).Received for publication May 7, 2004; accepted for publication May 8, 2004. ( Bartke et al, 1984;Matt et al, 1984). This latter effect is of particular interest, because the major shifts observed in the sensitivity of luteinizing hormone (LH) and FSH release to feedback control by gonadal steroids accompany annual cycles of reproductive activity in both sexes of many (presumably all) seasonal breeders and are critically important for transitions between reproductive activity and quiescence. Reduced sensitivity of the hypothalamus and the pituitary to negative feedback of sex steroids during annual reactivation of the gonads resembles the endocrine changes that take place during puberty in both seasonal and nonseasonal breeders, including humans.In the hamster testis, PRL, along with the gonadotropins, regulates the expression of its own receptors (Klemcke et al, 1984(Klemcke et al, , 1986Amador et al, 1985) and LH receptors (Bex et al, 1978; and enhances the responsiveness of Leydig cells to LH stim...

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Effects of induced hypoprolactinaemia in the ram : plasma gonadotrophin levels, LH and FSH receptors and histology of the testis

Cited by 15 publications

References 16 publications

Effects of bromocriptine administration during the follicular phase of the oestrous cycle on prolactin and gonadotrophin secretion and follicular dynamics in merino monovular ewes

Effects of bromocriptine administration during the follicular phase of the oestrous cycle on prolactin and gonadotrophin secretion and follicular dynamics in merino monovular ewes

Prolactin regulation of testosterone secretion and testes growth in DLS rams at the onset of seasonal testicular recrudescence

Prolactin in the Male: 25 Years Later

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