Effects of a hyperbaric environment on respiratory and monoamine oxidase activities.

The effects of a prolonged hyperbaric environment (21 ATA He-O2, 200 +/- 30 mm Hg O2, 32.5 +/- 1 degrees C) were investigated on the respiratory activity of rat liver homogenates and the activity of monoamine oxidase in isolated rat-liver preparations. Exposure to a hyperbaric environment for 84 days caused selective in vitro inhibition of nicotinamide adenine dinucleotide (NAD)-dependent oxidation of pyruvate, D-isocitrate, and alpha-ketoglutarate by rat-liver homogenates. The addition of NAD to the reaction mixture decreased the degree of such an inhibition. No effects on the in vitro activity of liver monoamine oxidase and its inhibition by pheniprazine were observed during exposure of animals to a prolonged high-pressure environment.