Correlation between ultrastructure and biochemical changes in the testis of the American grey squirrel, Sciurus...

Distinct differences in tha ability of isolated seminiferous tubules and interstitium to utilize steroid precursors for androgen production in vitro were observed during the reproductive cycle of the American grey squirrel, Sciurus carolinensis. In spermatogenically active testes, the seminiferous tubules and the interstitium readily synthesized androgens from labelled C21 steroid precursor; seminiferous tubules also produced significant amounts of 17alpha,20alpha-dihydroxyprogesterone. However, during sexual regression androgen synthesis was drastically reduced in both testicular components, while the production of 20alpha-reduced metabolites of progesterone and 17alpha-hydroxyprogesterone was increased. Many of the fine-structural changes occurring in Leydig and Sertoli cells during the reproductive cycle could be correlated with the capacity of isolated seminiferous tubules and interstitium to formulate androgens from labelled precursors.