Reflectance spectrophotometric monitoring of the isolated perfused heart as a method of measuring the oxidation-reduction state of cytochromes and oxygenation of myoglobin.

Reflectance spectrophotometry was assessed as a means of detecting metabolic oxidation-reduction changes in cytochromes and the oxygenation level of myoglobin in isolated perfused rat hearts. The movement artefact due to the heartbeat was largely eliminated by appropriate design of the optical geometry. A considerable myocardial oxygen gradient was detected using myoglobin deoxygenation as an indicator. The oxygenation level of myoglobin oscillated in pace with the contraction/relaxation cycle of the heart, deoxygenation occurring during the systole. The inconsistency in the previous reports on the myoglobin oxygenation and the problems of spectrophotometry of the beating heart are discussed.