COMPARATIVE IMMUNOCYTOCHEMICAL DEMONSTRATION OF G-PROTEINS IN RAT-HEART TISSUE

Localization of G proteins in the rat heart tissue was investigated us ing primary affinity-purified antibodies against synthetic peptides wi th amino acid sequences corresponding to alpha-subunits (alpha(i commo n) and alpha(i 1, 2)) of G proteins. Detection of immunoreactivity was performed with the peroxidase-anti-peroxidase complex (PAP), avidin-b iotin complex (ABC) and fluorescein-labelled secondary antibodies for light microscopy and the protein A-gold technique for electron microsc opy. In ventricles and atria, immunostaining for G proteins was detect ed in the sarcolemma and perinuclear space of cardiomyocytes. In endot heliocytes and fibroblasts, immunoreactivity was present also in the e ndoplasmic reticulum. All four immunocytochemical methods permit to de monstrate the same localization of G proteins in heart tissue. The ABC method and fluorescein labelled secondary antibodies technique showed the same sensitivity which is higher than that of the PAP method. Nom arski contrast microscopy enhanced the visualization of the final reac tion product formed by the peroxidase reaction developed with diaminob enzidine in the ABC method. The results are discussed in terms of the role of G proteins in signal transduction via plasma membrane and memb ranes of the intracysternal space of the cell.