Type B Atrial Natriuretic Peptide Receptor in Cardiac Myocyte Caveolae

Abstract We have previously shown that atrial natriuretic peptide (ANP) is present in caveolae of in situ rat atrial myocytes. To investigate whether intracaveolar ANP of rat atrial myocytes exists within caveolae bound to type B ANP receptors (ANP-RB, a guanylyl cyclase), we have used confocal immunofluorescence microscopy applied to primary cultures of atrial myocytes from adult rats and to freshly dissociated rat atrial myocytes (not cultured). These experimental designs tested whether atrial myocyte ANP-RB colocalizes at the plasmalemma and elsewhere in the cell with the muscle-specific isoform of the caveolar coating protein, caveolin-3, and with a fraction of cellular ANP. The experiments showed that cellular caveolin-3, a fraction of cellular ANP-RB, and a fraction of cellular ANP colocalize at the plasmalemma of cultured atrial myocytes and of freshly dissociated atrial myocytes. The observations support the hypothesis that in rat atrial myocytes, intracaveolar ANP is bound to ANP-RB, a protein wh...