Characteristics of energy metabolism in specialized muscle of bovine heart.

Characterization of the energy metabolism pattern of the specialized heart muscle of bovine heart was studied in comparison with that of the ordinary heart muscle. Mitochondrial oxygen consumption of the specialized heart muscle was significantly lower than that of the ordinary heart muscle with succinate as the substrate. On the other hand, there was no significant difference in oxygen consumption between both heart muscles with glutamate + malate as the substrates. The activity levels of succinate dehydrogenase and lactate dehydrogenase were much lower than those of the ordinary heart muscle. The isozyme pattern of LDH of the specialized heart muscle consisted of one major component of LDH-1 (H4) and that of the ordinary heart muscle consisted of two major components of LDH-1 (H4) and LDH-2 (H3M). The ratio of NADH to NAD of the specialized heart muscle was remarkably lower than that of the ordinary heart muscle. These results indicate that the specialized heart muscle depends not only upon anaerobic metabolism but also upon aerobic metabolism for its energy supply.