The cardiac function is exquisitely sensitive to oxygen, because its energy production mainly depends on the oxidative phosphorylation at mitochondria. Thus, oxygenation state of the tissue is critical. Cytochrome a,a3, hemoglobin and myoglobin, which play indispensable role in the oxygen metabolism, have the broad absorption band in near infrared (NIR) region and the light in this region easily penetrates biological tissues. Using NIR spectrophotometry, we attempted to measure the redox state of the copper in cytochrome a,a3 in rat heart through thoracic wall without open chest. The result is given in this paper.
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