The effect of stress induced by ether anaesthesia on cholesterol content and cholesteryl-esterase activity in rat-adrenal cortex.

Abstract

The cholesterol content and the activities of cholesteryl esterase and cyclic‐AMP‐dependent protein kinase have been studied in the adrenal glands of rats. These studies have been performed on the adrenal glands of rats injected with a protein‐synthesis inhibitor, cycloheximide, and in the adrenal glands of rats exposed to ether anaesthesia to increase the blood concentration of adrenocorticotrophic hormone.The analysis of the adrenal steroids revealed that acute stress induced by ether anaesthesia stimulated cholesterol ester depletion in adrenal lipid droplets. Cycloheximide injection into rats did not significantly alter the concentrations of cholesterol and cholesterol esters in the lipid droplets. Injection of cycloheximide followed by ether anaesthesia resulted in an increase in free cholesterol with a concomitant decrease in cholesterol ester concentration within the lipid droplets.Cholesteryl esterase and protein kinase activities in rat adrenal 105000 × g supernatant fractions were significantly higher in animals subjected to stress by ether anaesthesia. Injection of cycloheximide did not prevent the stress‐induced enhancement of the activities of either enzyme.Cholesteryl esterase activity was significantly enhanced by the addition of cyclic AMP, ATP and theophylline in the presence of cyclic‐AMP‐dependent protein kinase. The combination of all three activators proved to be more effective than any one or combinations of any two factors. The degree to which the activators stimulated cholesteryl esterase was higher in untreated animals than in animals subjected to ether anaesthesia.It is postulated that the enhancement of cholesteryl esterase activity induced by ether anaesthesia is due to the effect of adrenocorticotropic hormone on the adrenal gland, and that in vitro activation of cholesteryl esterase by cyclic AMP and ATP involves a protein‐kinase‐dependent phosphorylation reaction.Subcellular distribution of cholesteryl esterase activity in rat adrenal gland and some properties of the enzyme have been studied.