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

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Abstract
We have examined testicular and pituitary function in inbred CD-F rats and DBA7/2J 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 shamoperated; 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 < 0.001), LH levels were depressed (16 ± 3 vs. 59 ± 9 ng/ml; P < 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 < 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 < 0.02) and the adrenals (74 ± 3 vs 44 ± 2 mg; P < 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 < 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 < 0.01). In both rats and mice, chronic hyperprolactinemia did not affect plasma testosterone levels or testes weight and increased seminal vesicle weight.