CHARACTERIZATION OF THE CRUDE MEMBRANE-FRACTION OF CARDIOMYOCYTES USING ENZYME CYTOCHEMICAL MARKERS

The crude membrane fraction of cardiomyocytes, which had been used as the antigen for the study of autoantibodies against beta-adrenergic re ceptors, was characterized using cytochemical methods: in a reaction f or adenylate cyclase as an enzyme marker of the beta-receptors of plas ma membrane and in a reaction for glucose-6-phosphatase as an enzyme m arker of the sarcoplasmic reticulum. The specific precipitates of both enzyme reactions were localized on the membrane vesicles. In case of AC reaction the precipitate was observed on approximately 80% and in c ase of G-6-Pase on aproximately 25% of the whole amount of the vesicle s observed, indicating prevalence of vesicles of plasmalemmal origin. These results reveal that the used membrane fraction is appropriate fo r the study of autoantibodies against beta-receptors, but it can also contain other proteins (antigens) which can cross-react with autoantib odies against beta-adrenergic receptors.