Western blots of guinea pig total heart tissue, unpurified (crude), and percoll-gradient purified isolated cardiac mitochondria. Blots show levels of total heart iNOS and nNOS. However, purified isolated mitochondria (mito-β-tubulin, calnexin, SERCA2, and GM130 free), displayed only a low level of iNOS and absence of nNOS at approximately 150 kDa suggesting the unpurified, crude mitochondrial preparation could contain Golgi and SR attached MAM. VDAC1 was used to monitor mitochondria content.