Effects of high doses of leucine and ketoleucine on glycogen and protein metabolism in acute uremia.

Binephrectomized rats treated with high doses of ketoleucine (0.5 g/rat per 20 hr) expired after about 45 hr. In contrast, survival time was 100% 60 hr after ureteral ligation. In comparison to animals receiving low-protein diets, addition of leucine to the diet almost doubled muscle and liver protein content whereas ketoleucine increased liver protein during the first 40 hr after operation about 1.5-fold. Skeletal muscle protein content was enhanced in the ureter-ligated rats with administration of ketoleucine. There was also about a 10-fold elevation in liver glycogen and total carbohydrate content between the 20th and 60th hr in binephrectomized rats fed leucine at 5-hr intervals. In skeletal muscle glycogen, there were no significant differences among the acutely uremic rats fed at 10-hr intervals low-protein diets alone or supplemented with leucine or ketoleucine. Leucine inhibits glycogenolysis by lowering phosphorylase alpha activity in muscle and liver, whereas ketoleucine enhances glycogenolysis in acute uremia. In rats supplemented with letoleucine, there is a progressive inactivation of glycogen synthetase I which occurs in parallel with increasing phosphorylase alpha activity. In binephrectomized rats receiving leucine supplements at 5-hr feeding intervals, the activity of liver glycogen synthetase I increases up to a maximum of 90% of total enzyme activity.