Cytochemical methods for the localization of adenylate cyclase. A review and evaluation of the efficacy of the procedures.

The cytochemical procedures for localizing adenylate cyclase have been a source of controversy since their introduction. The importance of cyclic adenosine monophosphate (AMP), the product of adenylate cyclase's action on adenosine triphosphate (ATP), in cell biology is clear. Thus, the ability to localize this enzyme system reliably is an important tool in the study of various cellular functions. This report reviews the literature and presents a biochemical evaluation of the methods for localizing adenylate cyclase. The review and data presented serve to clarify many of the controversies surrounding this important cytochemical procedure. It is evident that although there are problems associated with localizing the enzyme, several valid procedures are currently available for the cytochemical localization of adenylate cyclase. In using these procedures, the effects of fixation and the capture agent on adenylate cyclase activity in the particular tissue being studied should be considered. Only repurified adenylyl imidodiphosphate [App(NH)p] should be used in the incubation medium. If care is taken, the use of these techniques can be of great value in the continued study of the role of cyclic nucleotides in cell biology.