A new spectroscopic approach to cardiac energy metabolism.

The optical characteristics of the hemoglobin-free perfused rat heart have been examined in detail. For dual-wavelength spectrophotometry, absorption pairs at 605-620 nm and 587-620 nm are found to be suited for the investigation of the oxidation-reduction changes of cytochrome aa3 and oxygenation-deoxygenation of myoglobin in cardiac tissue. Techniques by which the absorption changes of myoglobin and cytochrome aa3 can be measured during one cycle of contraction-relaxation are presented. The results demonstrate that, in the aerobic state, myoglobin is more oxygenated during the systolic and diastolic periods and deoxygenated in the resting period, whereas cytochrome aa3 is more reduced in the systole and diastole and oxidized in the resting period.