Localization of beta-hydroxysteroid dehydrogenase in Anguilla anguilla testis

The histochemical reaction for 3 beta-hydroxysteroid dehydrogenase was applied to glutaraldehyde fixed eel testis and successively processed for transmission electron microscopy. The reaction product was found only on the smooth endoplasmic reticulum and in the intermembrane space of mitochondria of the Leydig cells of hCG treated silver eels. The positive cytochemical reaction appears to be coupled with an enlargement of the Leydig cells and an increase of their smooth endoplasmic reticulum.