Effects of Experimentally-Induced Chronic Hyperprolactinemia on Testosterone and Gonadotropin Levels in Male Rats and Mice

Abstract

We have examined testicular and pituitary function in inbred CD-F rats and DBA/2J mice with chronic hyperprolactinemia induced by grafting 4 anterior pituitaries from adult females of the same strain under the kidney capsule. Eight rats were given pituitary isografts and 9 were sham-operated; blood samples were collected at 4-7 week intervals, and the animals were killed 6 months later. One month after surgery, PRL levels in grafted rats were elevated (348 +/- 15 vs. 94 +/- 11 ng/ml; P less than 0.001), LH levels were depressed (16 +/- 3 vs. 59 +/- 9 ng/ml; P less than 0.001), but T levels were not affected (1.0 +/- 0.1 vs. 1.1 +/- 0.2 ng/ml). The elevated PRL levels in grafted animals did not decline during the subsequent 5 months, while LH levels increased slightly, and T levels remained indistinguishable from those in the controls. At the time of autopsy, FSH levels were reduced in grafted rats (230 +/- 40 vs. 501 +/- 108 ng/ml; P less than 0.05). Multiple pituitary isografts did not affect the weight of the testes or the ventral prostate, but increased the weight of the seminal vesicles (P less than 0.001). In 11 mice examined 5.5 months after receiving pituitary isografts, plasma PRL levels were dramatically elevated (330 +/- 35 vs. 27 +/- 2 ng/ml; P less than 0.001), but plasma T levels and testicular weight were not different from those observed in 12 sham-operated controls. The weight of the seminal vesicles in grafted mice was increased (P less than 0.01). In both rats and mice, chronic hyperprolactinemia did not affect plasma testosterone levels or testes weight and increased seminal vesicle weight.

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

“…3c, d) A stimulating effect of bromocryptine treatment on FSH levels has also been reported in suckling ewes (Kann et al, 1977) and women (Seki et al, 1974 ;Nader et al, 1975). However, our results contrast with the increased release of FSH in hyperprolactinaemic rats (Voogt et al, 1969), dwarf mice (Bartke et al, 1977) and hamsters and also with the decreased secretion of FSH in men treated with bromocryptine (Lackritz and Bartke, 1980 (Rajaniemi et al, 1974 ;Charreau et al, 1977), as well as bromocryptine per se (Vermes and Telegdy, 1978) and FSH (Ketelslegers et a/., 1978) As suggested earlier (Barenton and Pelletier, 1980 ;Barenton, 1981) (Stolla et al, 1978) and mice (Bartke, 1974 …”

Effects of the dopamine agonist cabergoline on the pulsatile and TRH-induced secretion of prolactin, LH, and testosterone in male beagle dogs

“…Abnormally high prolactin concentrations have been found to inhibit gonadotrophin secretion in rats [45,46] and boars [30]. The mechanism of gonadotrophin suppression seems to be located in the hypothalamus, where the tonic GnRH activity is reduced by increased prolactin concentrations leading to an inhibition of the pulsatility of LH secretion [47].…”

Prolactin induces adrenal hypertrophy

“…Other investigators have reported that hyperprolactinemic rats and mice show an increase in absolute and relative adrenal weight (6,9,10). However, these reports did not refer to any histological changes in the adrenal glands.…”