Importance of the esterification process in adipose tissue metabolism as evidenced by cycloheximide

Cycloheximide: an adrenergic agent

Cycloheximide, a widely used inhibitor of protein synthesis, stimulates glycogenolysis, gluconeogenesis and ureogenesis in isolated rat hepatocytes. The effects of cycloheximide were compared to those of norepinephrine. Both agents, cycloheximide and norepinephrine, produced slight increases in the levels of cyclic AMP (30% increases) which were blocked by propranolol. Interestingly, it was found that the metabolic actions of norepinephrine and cycloheximide (stimulation of glycogenolysis, gluconeogenesis and ureogenesis) were only slightly diminished by the beta adrenergic antagonist propranolol but abolished by the selective alpha 1 adrenergic antagonist prazosin. The ability of cycloheximide to inhibit protein synthesis was not affected by either prazosin or propranolol. It is concluded that the stimulation of glycogenolysis, gluconeogenesis and ureogenesis by cycloheximide in rat hepatocytes, is an effect of the antibiotic independent of its ability to inhibit protein synthesis and that is mediated through activation of alpha 1 adrenoceptors. The adrenergic activity of cycloheximide should be considered when this drug is used as an inhibitor of protein synthesis.

Effect of cycloheximide on temperature regulation in rats

The effect of cycloheximide, an inhibitor of protein synthesis, on temperature regulation in afebrile rats was studied to determine whether its reported antipyretic effect might be attributable to a non-specific antimetabolic effect. Within 60 min after administration of cycloheximide (5 mg/kg IP) to female rats at ambient temperatures of 34, 25 and 15 degrees C, a significant decrease in colonic temperature was observed as compared with control rats administered saline IP. Measurements of rate of oxygen consumption showed that cycloheximide (5 mg/kg IP) significantly depressed the ability of rats to increase their heat production during a cold stress (15 degrees C). In the cold the rate of oxygen consumption increased 8.7 +/- 0.8 ml/min/kg0.75 in the control rats but only 1.8 +/- 0.9 ml/min/kg0.75 in the cycloheximide-treated rats. Since the thermoregulatory changes accompanying cold stress are similar to those observed during the genesis of fever, these data suggest that cycloheximide may have a general depressant effect on heat production rather than a specific antipyretic effect.