Cellular and subcellular compartmentalization of steroid metabolism in the rat testis

The following aspects are discussed in relation to the cellular and subcellular localization of steroid metabolism in the rat testis: (1) the localization of enzyme activities for steroid production in interstitial tissue and seminiferous tubules in intact cells and in isolated mitochondrial fractions: (2) steroid production by isolated cellular and subcellular fractions and by the intact testis in vivo; and (3) the effect of cofactors on steroid production by rat testis preparations in vitro. It is concluded that it is difficult to decide whether steroid production and the enzymes involved in steroid metabolism are restricted to specific compartments. Steroid production by the testis can, however, be quantitatively explained by that occurring in the isolated mitochondria of the interstitial tissue.