SUPERRESISTANCE AGAINST HYPOXIA AFTER PRELIMINARY ADAPTATION TO REPEATED STRESS

The study investigated the influence of adaptation to stress on resist ance to hypoxia. After rats were adaptated to moderate restraint stres s, they were anesthetized and exposed to 6% O-2. Adaptation increased tidal volume by 2.6-fold, lung and alveolar ventilation by 1.6- and 1. 8-fold, respectively, and O-2 consumption by 1.6-fold; limited lactate accumulation in the liver by 2-fold, in the heart by 34%, in the lung by 36%, and in the blood by 36%; and elevated pH. At the same time, p reliminary adaptation to stress inhibited the hypoxic activation of li polysis and peroxidation in all tissues. The concentration of lipid pe roxides decreased after adaptation by 1.3- to 1.5-fold in different or gans, whereas the content of free fatty acids diminished by 1.7- to 2. 3-fold. Finally, after adaptation, mortality decreased under severe hy poxia by 6.5-fold. Thus, the data suggest that the cross-protective ef fect of adaptation was achieved by the economization of respiration an d circulation, by marked augmentation in the ability of tissues to uti lize blood O-2, and by the limitation of processes that are able to da mage tissue membranes, namely, acidosis, lipolysis, and lipid peroxida tion.