Delayed reproductive regression in male hamsters bearing intrarenal pituitary homografts and kept under natural winter photoperiods.

The testes and accessory sex organs of adult male hamsters regressed to an infantile state when the animals were maintained under natural photoperiodic and temperature conditions beginning November 13. The atrophy was evident after both five and ten weeks exposure to these conditions. Either one or two prolactin-secreting pituitary grafts placed under the kidney capsule greatly delayed the testicular and accessory organ regression. Animals bearing pituitary grafts also had higher circulating levels of immunoreactive prolactin while plasma luteinizing hormone values were similar in all groups of hamsters.