[Brain tissue respiration after exposing rats in hyperoxic helium-oxygen mixtures at atmospheric and increased pressure].

Experiments on Wistar rats showed that their 5-hour exposure to He-O2 atmospheres (at comfortable temperature) did not affect metabolic rates in the mitochondria of the brain cortex. In this case the partial pressures of oxygen were 0.21 and 0.40 kg/cm2 at a normal and elevated (40 kg/cm2) total pressure. Further increase of pO2 to 0.60 kg/cm2 induced of mitochondrial respiration and oxidative phosphorylation. The rat exposure to 100% O2 atmosphere at a normal pressure resulted in a decrease of metabolic rates and uncoupling of respiration and oxidative phosphorylation processes. The rat exposure to He-O2 atmospheres at an elevated total pressure (40 kg/cm2) with the partial pressures of oxygen of 0.21 and 0.30 kg/cm2 did not alter mitochondrial respiration and oxidative phosphorylation. However, the exposure to higher partial pressures of oxygen--0.40 and especially 0.60 kg/cm2--inhibited the above processes.