Effects of Chronic Hyperprolactinemia in Mice on Plasma Gonadotropin Concentrations and Testicular Human Chorionic Gonadotropin Binding Sites*

Effects of artificially induced hyperprolactinemia in male DBA/2 mice were studied by transplanting four pituitary glands under the kidney capsules. After 52--57 days the animals were sacrificed, and tissue and plasma samples were obtained. Plasma concentrations of FSH and LH were significantly higher in pituitary-grafted mice than in sham-operated controls. Testicular LH/human chorionic gonadotropin (hCG) binding, measured via use of [125I]iodo-hCG, was significantly depressed both on a per milligram protein and per testes basis in hyperprolactinemic mice. Coincident with decreased hCG binding was a significantly diminished ability of decapsulated testes to produce testosterone in response to hCG in vitro. However, testosterone production by unstimulated hyperprolactinemic mouse testes was normal. Significantly increased body, seminal vesicle, and adrenal weights were also present in hyperprolactinemic mice. The data indicate that hyperprolactinemia in mice is associated with decreased testicular LH/hCG binding and a concomitant decrease in the responsiveness to hCG in vitro. These actions may be mediated by increased plasma LH concentrations.