[Effect of a prolonged stay in space on the reaction of the adrenal cortical and medullary layers].

Concentrations of corticosteron and catecholamines, and activities of catecholamine synthesizing enzymes, tyrosine hydroxylase, dopamine-beta-hydroxylase and phenyl ethanol amine-N-methyl-transferase, were measured in the adrenals of rats flown for 19.5 days aboard the biosatellite Cosmos-782, synchronous and vivarium control animals sacrificed on R + 0 and R + 26 days. The flown rats showed a moderate but significant increase in the adrenal weight, corticosteron concentration and tyrosine hydroxylase activity on R+0 day. These parameters returned to the normal on R+26 day. This data gives evidence that the adrenocortical and sympathoadrenal systems were not significantly stimulated by the space flight effects; therefore, weightlessness cannot be considered as a potent stressful agent, although its some stressogenic effect has been documented.