[Oxygen tension in the brain cortex arterioles during spontaneous respiration with the hypoxic gas mixture in rats]

Hypoxic exposure of Wistar rats resulted in sharp fall of the blood oxygen saturation on 1st-5th branching order arterioles. The increased oxygen extraction at hypoxia is due to an intensive diffusion of the oxygen through the walls of the arterioles and a lowered blood flow in the brain microvessels. Permeability of the arterioles' walls for oxygen plays a negative role as it lowers the oxygen tension in the blood entering the capillaries.