Changes in trout testis cyclic GMP concentration during hormonally induced spermatogenesis.

The concentration of cyclic GMP was determined in trout testes (Salmo gairdnerii) during hormonally-induced sermatogenesis. Early in spermatogenesis, a relatively high concentration (1 mumole/kg wet weight testis) of cyclic GMP was present. A sharp, ten-fold, decrease in testis cyclic GMP concentration occurred during the early stages of rapid mitotic activity and testis growth. A further gradual five-fold decrease in cyclic GMP concentration occurred during meiosis and the following transformation of spermatocytes into spermatids and then to mature spermatozoa.