AJP - Renal Physiology, Vol 241, Issue 3 257-F262, Copyright © 1981 by American Physiological Society
Spectrophotometric monitoring of O2 delivery to the exposed rat kidney
R. S. Balaban and A. L. Sylvia
Optical spectrophotometry was used to measure changes in the
oxidation-reduction state of cytochrome c oxidase in the in situ rat
kidney. Alterations in the redox state of cytochrome c oxidase were
monitored during variations in the amount of oxygen being delivered to the
animal. Spectral analyses were performed on whole kidney, cortical tubule
suspensions, and blood (the latter flowing freely through surgically
implanted femoral arteriovenous shunts). Reaction spectra identified the
location of the absorption maxima for reduced cytochrome c oxidase to be at
approx. 605 nm. Additional spectral analysis indicated that hemoglobin
oxygenation-deoxygenation changes had minimal artifactual interference on
the cytochrome redox signals. The present results indicate that
mitochondrial cytochrome c oxidase is not maximally oxidized in the in situ
kidney of anesthetized rats at arterial oxygen in the in situ kidney of
anesthetized rats at arterial oxygen tensions within the normal
physiological range. The redox state of the enzyme in vivo is altered by
changes in the level of inspired oxygen over a wide range. The current data
are consistent with the existence of nonuniform regions of aerobic
respiration occurring in the in situ kidney.
