Oxidative metabolism of cultured adult cardiomyocytes.

Cultured adult cardiomyocytes from rat exhibit, if unstimulated, low rates of substrate oxidation, corresponding to their mechanical inactivity. They oxidize exogenous fatty acids and lactate preferentially to glucose. Endogenous lipolysis provides the largest portion of oxidative substrates. Pyruvate dehydrogenase is largely in its inactive form. If glucose is the sole exogenous substrate, the quiescent cells produce lactate as a purely aerobic phenomenon probably reflecting the reduced state of the cytosol at low respiration rates.