Localization of cyclic GMP and cyclic AMP in cardiac and skeletal muscle: immunocytochemical demonstration.

When rat cardiac and skeletal muscle are explored by immunocytochemical procedures designed to show sites of localization of adenosine 3',5'-monophosphate (cyclic AMP) and guanosine 3',5'-monophosphate (cyclic GMP), distinct staining patterns for the two nucleotides are seen. Antibody to cyclic AMP is found in the area of the sarcoplasmic reticulum, while antibody to cyclic GMP is found with a periodic distribution corresponding to that of the A band. This suggests a role for cyclic GMP in the regulation of myosin.