We determined the contribution of all major energy substrates (glucose, glycogen, lactate,
oleate, and triglycerides) during an acute increase in heart work (1 μm epinephrine,
afterload increased by 40%) and the involvement of key regulatory enzymes, using isolated
working rat hearts exhibiting physiologic values for contractile performance and oxygen
consumption. We accounted for oxygen consumption quantitatively from the rates of
substrate oxidation, measured on a minute-to-minute basis. Total β-oxidation (but not …