Copper Content and Exchange in Mammalian Hearts

Determination of the copper (Cu) content of rat, rabbit, and mouse hearts proved to be a sensitive microassay for mitochondria] content and membrane area of mitochondrial cristae per unit myocardial cell volume. The direction of variations in Cu content corre-lated well with variations in membrane area of mitochondrial cristae determined by mor-phometry of electron micrographs during normal postnatal growth, ventricular hypertro-phy after aortic constriction, and thyroxin-stimulated myocardial cell growth. Right and left ventricular and interventricular septal Cu contents per unit dry weight were the same, did not vary during postnatal growth, and significantly exceeded atrial Cu content. Among different mammalian species, ventricular Cu content per unit dry weight tended to vary inversely with adult animal size and thus with adult resting heart rate. The existence of mechanisms for transport of "Cu across the myocardial cell plasma membrane and for in-corporation of "Cu into mitochondrial cristae from an intracellular precursor pool was demonstrated by injecting "Cu-labeled blood serum into rats. KEY WORDS myocardial copper content cytochrome oxidas