[Ultrastructural demonstration of 3 beta-hydroxysteroid dehydrogenase activity using potassium ferricyanide]

Sections of Rat and Amphibian adrenocortical tissue fixed in a mixture of 1% formaldehyde and 0.25% glutaraldehyde, are incubated in a medium containing namely a 3 beta-hydroxysteroid (substrate), NAD, potassium ferricyanide (hydrogen acceptor) and copper sulfate. A hyaloplasmic copper ferrocyanide precipitate is observed in the immediate vicinity of the smooth endoplasmic reticulum membranes, or in close contact with them. This reaction, which does not occur in media lacking the substrate or containing cyanoketone, is a result of 3 beta-hydroxysteroid dehydrogenase activity. Problems concerning the precise localization of this enzyme are discussed.