Guanylyl cyclase (GC)-A and GC-B activities in ventricles and cardiomyocytes from failed and non-failed human hearts: GC-A is inactive in the failed cardiomyocyte

► Membranes from human heart left ventricles express half as much GC-B activity as GC-A. ► In failing human ventricles, CNP-GC-B-dependent activity was significantly increased. ► Human cardiomyocytes express GC-A but little or no GC-B. ► GC-A is expressed at reduced levels compared to expression in other cells in the ventricle. ► GC-A in cardiomyocyte-enriched samples from failing human hearts is refractory to ANP.