PROLONGED EXPOSURE TO HALOTHANE AND ASSOCIATED CHANGES IN CARBOHYDRATE-METABOLISM IN RAT MUSCLES IN-VIVO

Halothane, an anesthetic presently used in animal experimentation, is reported to stimulate glycogen breakdown in isolated preparations of r at skeletal muscles, suggesting that it may not be a suitable anesthet ic for the study of glycogen metabolism in rats in vivo. The purpose o f this study was to establish whether prolonged exposure to halothane in rats in vivo is associated with accelerated glycogenolysis. Exposur e of rats to halothane for up to 1 h was not accompanied by either any change in the levels of glycogen or increase in activity ratios of gl ycogen phosphorylase in muscles, irrespective of their fiber compositi ons. In marked contrast, the levels of lactate, inorganic phosphate, g lucose l-phosphate, glucose B-phosphate, fructose 1,6-bisphosphate, an d fructose 2,6-bisphosphate changed progressively during anesthesia. A ccordingly, the interpretation of muscle metabolite levels must be per formed with caution in experiments involving prolonged exposure to hal othane. Overall, our findings indicate that the reported halothane-med iated stimulation of glycogen breakdown in vitro is likely to be an ar tifact and that halothane is a suitable anesthetic for experiments con cerned with glycogen metabolism in rats.