The effects of adrenal corticosteroids on oxygen utilization in rats

1. Sham-adrenalectomized and cortisol injected adrenalectomized rats survived exposure to a hypoxic (5% oxygen) atmosphere significantly longer than did adrenalectomized control rats. 2. The difference in survival times between rates with and without corticosteroids was not due to the absence of the adrenal medulla since sham-hypophysectomized rats' survived exposure to a hypoxic (5% oxygen) atmosphere significantly longer did hypophysectomized. 3. Rats, with and without adrenal corticosteroids, when exposed to a 5% oxygen atmosphere for one hour showed significant elevation in blood lactic acid concentration. More significant, however, was the findings that rats with adrenal corticosteroids had significantly lower levels of blood lactic acid under hypoxic conditions than those without. 4. Cortisol treatment of adrenalectomized rats produce a significant elevation of cerebral cortical mitrochondrial state 3 respiration, respiratory control ration and ADP:0 ratio when NAD-linked substrates were used. Succinate, a substrate not linked to NAD, showed non-rate limiting decrease in state 3 respiration and respiratory control ratio after cortisol treatment. Cycloheximide and Actinomycin D had no effect on these parameters of mitochondrial respiration, but were capable of blocking cortisol induced changes. 5. The rotenone sensitive factor of the NADH dehydrogenase complex was elevated by cortisol treatment from 0.09 to 0.14 nmoles/mg protein. The cytochrome content of the mitochondrial respiratory chain was not altered by corticosteroids, suggesting that the cortisol induces increases in state e respiration and respiratory control ratio with NAD-linked substrate are due to an increase in the concentration of the rotenone sensitive factor.