Effects of different numbers of ectopic pituitary transplants on regulation of testicular LH/hCG and prolactin receptors in the hamster (Mesocricetus auratus).

Adult male hamsters were given transplants of 1/2, 1, 2, 3 or 4 pituitaries under the kidney capsule and were killed 4 weeks later. Pituitary transplants produced a significant, dose-related increase in plasma prolactin levels, no changes in plasma LH and an increase in plasma FSH. Concentration of LH/hCG receptors in the testes was significantly increased in animals with 2 or 3 transplants and concentration of testicular prolactin receptors was significantly increased in those given 2 transplants. The apparent stimulatory effects of 1/2, 1 or 4 transplants on testicular LH/hCG and prolactin binding were not statistically significant. Some of the animals were injected with 0.3 i.u. hCG/g body weight 24 h before being killed. This produced a significant reduction in the levels of prolactin receptors and an apparent reduction in the levels of LH/hCG receptors in the testes. Elevation of plasma testosterone concentrations in response to hCG was significantly greater in animals given 3 or 4 pituitary transplants than in the remaining groups. These results provide further evidence that prolactin increases the number of LH/hCG and prolactin receptors in the hamster testis and suggest that changing the number of ectopic pituitary transplants may result in biphasic effects on the testis, with 2 or 3 transplants being maximally stimulatory.