Immunocytochemical localization of G-proteins (alpha subunits) in rat heart tissue

The subcellular localization of peptide antibodies against G-protein alpha subunits was studied by the indirect immunogold technique with Lowicryl K4M embedded rat cardiac tissue. Two antibodies were used. The alpha common peptide antibody recognizes the alpha subunits of Gs, Gi and Go. The alpha i common peptide antibodies recognize the alpha subunits of all Gi alpha subtypes (G1-3). Immunoreactivity against alpha common and alpha i common antibodies was found along the cell surface of cardiomyocytes and endothelial cells. No immunoreactivity was seen on sarcoplasmic reticulum membranes. T-tubule membranes showed a little reactivity. Distribution patterns obtained with alpha common and alpha i common antibodies were identical. Immunogold was seen in cardiocytes from both atria and ventricles. In light-microscopical studies with peroxidase-conjugated secondary antibodies, heavy immunostaining was seen in SA and AV nodes.