Biology of Reproduction, Vol 28, 167-177, Copyright © 1983 by Society for the Study of Reproduction

ARTICLES

Effects of hyper- and hypoprolactinemia on gonadotropin secretion, rat testicular luteinizing hormone/human chorionic gonadotropin receptors and testosterone production by isolated Leydig cells

C Waeber, O Reymond, M Reymond and T Lemarchand-Beraud

The effect of prolactin (Prl) on gonadotropin secretion, testicular luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptors, and testosterone (T) production by isolated Leydig cells has been studied in 60-day-old rats treated for 4 days, 4 and 8 weeks with sulpiride (SLP), a dopaminergic antagonist, or for 4 days and 4 weeks with bromocriptine (CB), a dopaminergic agonist. Plasma Prl concentrations were significantly greater in the SLP groups (204 +/- 6 ng/ml) and lower in the CB groups (3.0 +/- 0.2 ng/ml) than those measured in the control groups (54 +/- 6 ng/ml). The plasma concentrations of gonadotropin were not affected by a 4-day treatment with SLP or CB, nor were they after a 4-week treatment with CB. However, the hyperprolactinemia induced by an 8-week treatment with SLP was associated with a reduced secretion of gonadotropin (LH, 16 +/- 4 vs. 35 +/- 6 ng/ml; FSH, 166 +/- 12 vs. 307 +/- 14 ng/ml). In SLP- induced hyperprolactinemia, a 30% increase in the density of the LH/hCG testicular binding sites was observed (178 +/- 12 fmol/mg protein), whereas a 60% decrease was measured in hypoprolactinemia (55 +/- 5 vs. control 133 +/- 5 fmol/mg protein). Plasma T levels were increased in 4- day and 4-week hyperprolactinemic animals (4.3 +/- 0.4 and 3.9 +/- 0.4 ng/ml, respectively), but returned to normal levels in the 8-week group (3.0 +/- 0.5 vs. C: 2.3 +/- 0.2 ng/ml). No T modifications were observed in hypoprolactinemic animals. Two distinct populations of Leydig cells (I and II) were obtained by centrifugation of dispersed testicular cells on a 0-45% continuous Metrizamide gradient. Both possess LH/hCG binding sites. However, the T production from Leydig cells of population II increased in the presence of hCG, whereas that of cell population I which also contain immature germinal cells did not respond. The basal and stimulated T secretions from cell populations I and II obtained from CB-treated animals were similar to controls, whereas from 4 days to 8 weeks of hyperprolactinemia, basal and hCG induced T productions from cell population II decreased progressively. These data show that hyperprolactinemia causes, in a time-dependent manner, a trophic effect on the density of LH/hCG testicular receptors; reduces basal and hCG-stimulated T production from isolated Leydig cells type II; and results in an elevated plasma T concentration which decreases with time. The latter suggests a slower T catabolism and/or an impaired peripheral conversion of T into 5 alpha-dihydrotestosterone (DHT). Although hypoprolactinemia is associated with a marked reduction in testicular LH receptors, it does not affect T production.

This article has been cited by other articles:

				V. L. Williams, A. DeGuzman, H. Dang, M. Kawaminami, T. W. C. Ho, D. G. Carter, and A. M. Walker Common and specific effects of the two major forms of prolactin in the rat testis Am J Physiol Endocrinol Metab, December 1, 2007; 293(6): E1795 - E1803. [Abstract] [Full Text] [PDF]

				M. J. LeBaron, T. J. Ahonen, M. T. Nevalainen, and H. Rui In Vivo Response-Based Identification of Direct Hormone Target Cell Populations Using High-Density Tissue Arrays Endocrinology, March 1, 2007; 148(3): 989 - 1008. [Abstract] [Full Text] [PDF]

				P W Harvey, D J Everett, and C J Springall Hyperprolactinaemia as an adverse effect in regulatory and clinical toxicology: role in breast and prostate cancer Human and Experimental Toxicology, July 1, 2006; 25(7): 395 - 404. [Abstract] [PDF]

				P. R. Manna, T. El-Hefnawy, J. Kero, and I. T. Huhtaniemi Biphasic Action of Prolactin in the Regulation of Murine Leydig Tumor Cell Functions Endocrinology, January 1, 2001; 142(1): 308 - 318. [Abstract] [Full Text] [PDF]