Observing the deoxy myoglobin and hemoglobin signals from rat myocardium in situ.

1H NMR proximal histidyl NdeltaH signals of deoxy hemoglobin (Hb) and myoglobin (Mb) are distinguishable in the rat myocardium in situ. In the normoxic resting state, the blood and tissue pO2 is sufficient to saturate both Mb and Hb. No deoxy Mb or Hb signals are detected. Under 12% inspired O2, the erythrocyte Hb is partially desaturated and yields the alpha and beta proximal histidyl NdeltaH signals of deoxy Hb. The detection of the Hb signals clarifies the debate about the NMR visibility of erythrocyte Hb in vivo and augments the strategy to observe tissue pO2.