Role of oxygen in limiting respiration in the in situ myocardium

¹H NMR has now detected the proximal histidyl N(δ)H myoglobin (Mb) signal from the myocardium in situ. Upon ligation of the left anterior descending coronary artery in the rat myocardium, the deoxy Mb signal appears at 78 ppm During dopamine infusion at up to 80 μg/kg/min, the heart rate pressure product (RPP) increases by a factor of 2, the phosphocreatine (PCr) decreases by 17%, and the ratio of the change in inorganic phosphate over PCr (ΔP(i)/PCr) increases by 0.2. However, no deoxy myoglobin signal is detected. Oxygen availability does not appear to limit oxygen consumption nor oxidative phosphorylation under dopamine enhanced work state in myocardium.