[Non-invasive assessment of mitochondrial function in rat brain during and after hemorrhagic shock].

Brain oxygen metabolism was studied noninvasively by the simultaneous measurement of hemoglobin (Hb) oxygenation, and cytochrome oxidase (aa3) redox state in the brain of a rat, using our near-infrared (NIR) transmission spectrophotometer. Redox state of cyt. aa3 was measured using a wavelength pair of 830-940 nm. The changes of oxy- and total (oxy + deoxy) Hb content in the rat brain could be monitored quantitatively by expressions of -1.15 delta A750 + 1.39 delta A780 and -0.29 delta A750 + 0.59 delta A780, respectively (delta A750, delta A780: absorbance changes at wavelength 750 and 780 nm). An application of NIR-Spectrophotometry for the studies of brain metabolism in acute hemorrhagic shock in rats was presented. Tissue hypoxia was induced in 20 rats by rapid withdrawal of arterial blood to a mean blood pressure of 30 mmHg. This level of shock pressure was maintained for 30 minutes in group A (n = 8), and for 70 minutes in group B (n = 10), then the removed blood was returned by infusion. Blood oxygenation level, relative blood volume and cyt. aa3 redox state in the rat brain were monitored during shock, and for two more hours after the reinfusion. Group A had a high survival rate while group B had a poor survival rate. In both groups with the onset of hypotension, there occurred a rapid deoxygenation of brain blood and a rapid and progressive shift of cyt. aa3 towards a more reduced state.(ABSTRACT TRUNCATED AT 250 WORDS)