Prolactin (PRL), Follicle-Stimulating Hormone, and Luteinizing Hormone Are Regulators of Testicular PRL Receptors in Golden Hamsters

The ability of PRL, FSH, and LH to regulate testicular PRL receptors in golden hamsters was evaluated using a variety of experimental protocols. Exposure to a photoperiod of 5 h of light and 19 h of darkness (5L:19D) for 11 weeks precipitated a 94% reduction in content (femtomoles per testes) of testicular PRL receptors and, concomitantly, a decrease (P < 0.05) in plasma PRL, but not LH or FSH. One pituitary gland under the kidney capsule in 5L:19D-housed hamsters increased (P < 0.05) both the concentration (femtomoles per mg protein) and content of PRL receptors, as well as those of plasma PRL and FSH. Similar treatment in 14L:10D-housed hamsters produced comparable changes in plasma PRL and FSH without affecting PRL receptors. Injections of l-dopa for 7 days into hamsters housed in 5L:19D for 11 weeks significantly elevated serum FSH concentrations, had no measurable effect on serum PRL and LH, and induced a greater than 2-fold increase in PRL receptor levels. In a separate study, hamsters housed in 5L:...