Hormones and the differentiation of type A spermatogonia in mouse cryptorchid testes incubated in vitro.

In order to study hormonal effects on testicular germ cell differentiation, especially on type A spermatogonia, artificially induced cryptorchid testes of adult mice were cultured in a medium containing testosterone, dihydrotestosterone, tri-iodothyronine, dibutyryl 3':5' cyclic adenosine monophosphate, human chorionic gonadotrophin, LH, FSH, insulin and transferrin. These substances, with the exception of FSH, showed no stimulatory effect on the differentiation of type A spermatogonia. However, FSH activated cell division in type A spermatogonia and stimulated them to differentiate, while LH showed neither the promotion of differentiation nor a synergistic effect on FSH-mediated germ cell differentiation.