Treatment of atrial HL-1 cardiomyocytes with mutANP (B) and BNP oligomers (C) but not ANP oligomers (A) caused a substantial reduction in TOMM20 immunostaining (boxed region in upper panel [scale bar, 20μm] shown in inset in lower panel [scale bar, 5μm]). D. Exposure of cardiomyocytes to mutANP and BNP oligomers caused intracellular O2•− generation (scale bar, 50μm). E-G. mRNA levels are illustrated for genes encoding PGC-1α and NRF1 (normalized for control [CTL] values) following atrial cell treatment with monomers or oligomers prepared from ANP (E), mutANP (F) and BNP (D). N=4-6 biological replicates for each treatment (3 technical replicates each); *P<0.05 vs. control, Mann-Whitney test.