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White rats exposed to low temperature (5-7 degrees C) over 80 days showed a slow growth of the body weight and liver, lowering of liver glycogen and cholesterol content, increase in the relative weight of the thyroid gland and in the nuclei size of adrenal medulla, fall of blood 11-HOCS level, change in the mitotic phase ratio in the epithelium of the tongue and cornea, and an increase in the number of pathological mitoses in the cornea. A great number of changes did not appear fully reversible after the discontinuation of the exposure to low temperatures.

Pretreatment of rats with hydrocortisone or protamin-Zn-insulin within 4 days altered in subsequent acute hypoxia (3 hrs, "height" 10 000 m) the isoenzyme spectrum of LDH in lungs, liver tissue and kidney cortex. The differences in alterations in the activity and content of LDH isoenzymes were observed in tissues with various types of metabolism.

Metabolic activity of rat lungs were studied in normal state and in acute hypoxia, caused by an effect of rarefied atmosphere (3 hrs, "height" 10,000 m). Glycolytic splitting of carbohydrates and catabolism of proteins were increased in lungs under hypoxic stress. In hypoxia activities of adlobase, pyruvate kinase, succinate dehydrogenase, 5-hydroxytryptophan decarboxylase were increased, but hexokinase activity was decreased. Activities of lipase, lactate dehydrogenase and NAD-dependent malate dehydrogenase were not altered, whereas the ratio in specific activity of cytoplasmic malate dehydrogenase and lactate dehydrogenase was decreased.

The activities of gluconeogenic enzymes of the rat kidney cortex was studied after exposure to lowered atmospheric pressure (200 mm Hg) for 3 hours. The hypoxic stress was found to cause an increase in the activities of phosphoenolpyruvate carboxykinase and alanine aminotransferase, but failed to affect significantly the activities of fructose-1,6-diphosphatase, glucose-6-phosphatase, and aspartate aminotranspherase. The ratio of glucose-6-phosphatase/hexokinase activities was increased under these conditions.