The cytochrome oxidase redox state in vivo.

Abstract

The CuA redox centre of cytochrome oxidase has a distinct redox-sensitive absorbance band in the near infrared that enables it to be detected non-invasively (Jobsis 1977). We have been recently developing novel in vitro (Matcher et al. 1995) and in vivo (Cooper et al. 1996a) tests for the validity of algorithms claiming to be able to measure these redox changes, successfully deconvoluted from the greater spectroscopic perturbations induced by haemoglobin oxygenation and concentration changes. However, even if this problem is solved completely there still remains the question as to what the redox state of this metal centre is actually telling us about mitochondrial function in vivo. We are therefore performing parallel in vitro studies of the effect of energization, electron flow and oxygen tension on the redox state of CuA, similar to those originally outlined by Chance as aids to understanding NADH surface fluorescence measurements (Chance et al. 1973). This paper studies the effect of varying the rate of electron entry to cytochrome oxidase on the CuA redox state in vivo and in vivo and therefore relates to the value of the normal, physiological oxidation state of CuA.