Western blots of guinea pig total cardiac tissue, purified cardiac and liver mitochondria, and mitochondrial membrane (mito memb) with anti-iNOS specific primary antibody ab3523 (abcam). β-tubulin was used to assess purity of isolated mitochondria; VDAC1 was used to monitor mitochondria content. iNOS was faintly detectable in IMM (A), undetectable in isolated cardiac mitochondria (B,C), but strongly detectable in total heart tissue (C). Prior treatment of guinea pigs with lipopolysaccharide (LPS) did not appear to enhance band density of iNOS in heart mitochondria (A,B). Mito indicates mitochondria isolated from two hearts.