[Indices of human blood acid-base equilibrium and enzymatic activity in short-term antiorthostatic hypokinesia].

Before and after a 5 day head-down tilt of 4.5 degrees blood samples were withdrawn from different areas of the cardiovascular system of healthy male volunteers. Blood was sampled by means of selective catheterization. Parameters of acid-base equilibrium and activities of aminotransferases and alkaline phosphatase were measured. After immobilization the most significant changes were observed in the blood outflowing from the brain in which significant metabolic acidosis and increased activity of aspartate aminotransferase occurred. A slight increase in the activity of aspartate aminotransferase was also observed in the blood outflowing from the liver and kidneys. It is concluded that brain is the organ which is subjected to short-term simulated weightlessness in the highest degree.