Cerebral bioenergetics and in vivo cytochrome c oxidase redox relationships

Discovery of the near-infrared window into the body and the early development of near-infrared spectroscopy

Extension of optical monitoring of intact tissues from the visible and ultraviolet to the near-infrared (NIR) range (700-1300 nm) was first undertaken in 1977 for the purpose of monitoring the redox behavior of Cytochrome c oxidase (cyt c ox) in vivo. Soon it became evident that the much greater NIR translucency of skin and bone made it possible to reach brain and muscle tissue without surgical intervention. The presence of hemoglobin absorption led to complications forcing the construction of algorithms to separate the signals of the two molecular entities. It was also realized, however, that the hemoglobin signals provide information regarding the source of oxygen in the tissue, while the cyt c ox signals indicate the intracellular availability of oxygen for oxidative phosphorylation. This ability of recognizing the source/sink relationship greatly enhances the value of NIR spectrophotometry (NIRS) for research and clinical purposes. © 1999 Society of Photo-Optical Instrumentation Engineers.

Non-invasive measurement of respiratory chain dysfunction following hypothermic renal storage and transplantation

Ischemia/reperfusion (IR) damage is a major cause of dysfunction in transplanted organs. The objective of the present study was to correlate in vivo measurements of respiratory chain (RC) function with histological and physiological parameters. Non-invasive in situ (surface fluorescence) measurements of mitochondrial NADH and near infrared spectroscopic measurements of cyt aa3 were made in unstored (Group 1) and 72 hour stored (1 to 2 degrees C) (Group 2) autografted rabbit kidneys. The effect of sodium pentobarbitone on NADH levels was investigated. In Group 1, there was a significant change in the redox state of cyt aa3 in all (N = 6) kidneys on reperfusion which correlated with organ viability and increased NADH oxidation and minimal edema on histological examination. In Group 2 there was no significant change in cyt aa3 compared to baseline, and this correlated with poor long term organ viability, slower NADH oxidation, and severe cortical edema. Pentobarbitone inhibition of the RC resulted in rapid and complete reduction of NAD+ in Group 1, but none or only a slight reduction in Group 2. The results demonstrate that it might be possible in future to predict organ viability and histological changes by non-invasive measurements of RC dysfunction in the clinical transplant situation.

MRI quantitation of edema in focal cerebral ischemia in cats: correlation with cytochrome aa3 oxidation state

1H MRI permits detection of edema in the brain. In a middle cerebral artery stroke model in the cat, we found a significant correlation between an edema index based on MRI and a sensitive metabolic index of ischemia, the in vivo oxidation status of mitochondrial cytochrome aa3 determined by near-infrared reflectance spectrophotometry (r = -0.70, alpha = 0.001). This result suggests that a simple, noninvasive study using MRI can provide an index of the extent of ischemic damage in an experimental acute stroke model.