Adenosine triphosphatases in electroreceptor organs (ampullary organs and mormyromasts) of Gnathonemus petersii Mormyridae.

Cytochemical techniques were used for the light and electron microscopical localization of ATPase in the ampullary organ and the mormyromast, both cutaneous electroreceptors in Gnathonemus petersii (Mormyridae). At the right microscope level, two different techniques gave the same results, namely that high concentrations of the enzyme are present in the mormyromast and certain epidermal cells and weak concentrations in the ampullary organ. The enzyme was localized at the ultrastructural level using the lead capture method. It was found in the cytoplasm of type III accessory cells of the ampullary organ, in the apical cytoplasm of SC1 sensory cells and the accessory cells surrounding them and on the membrane of the SC2 sensory cells of the mormyromast. The ATPase of these various cells was inhibited by p-chloromercuribenzoate. The enzyme in the mormyromast SC1 and their accessory cells was not dependent on Mg2+ ions. However, that in the type III accessory cells of the ampullary organ and in the SC2 of the mormyromast was strictly dependent on Mg2+. In addition, there was a Ca2+-dependent ATPase in the microvilli of the SC2 of certain mormyromasts.