The testicular response to hemicastration in the male rat cannot be maintained in vitro.

The testicular response to hemicastration (in which testicular vein testosterone from the remaining testis doubles in concentration) was studied in vitro in order to establish whether the response is maintained after testicular tissue is removed from the animal. Decapsulated testes and collagenase-dispersed cells from decapsulated testes of rats were incubated for 24 h after hemicastration and testosterone production was compared with that in tissue collected at the time of surgery. Testosterone concentration in the remaining testis 24 h after hemicastration was significantly (P less than 0.05) higher than in the testis removed at the time of hemicastration, but testosterone production in vitro was similar in both tissues. Apparently the single testis remaining in a hemicastrated rat requires extratesticular support in order to maintain its stimulated state.