Effect of acute exercise on insulin generation of pyruvate dehydrogenase activator by rat liver and adipocyte plasma membranes.

Groups of young adult rats with body weights of 125-135 g (group A) or 300-400 g (group B) were subjected to one bout of prolonged exercise to exhaustion on a treadmill and were studied 2 h postexercise. Liver glycogen levels were markedly depleted in the exercised rats. Adipocytes from group A exercised rats showed a significantly greater increase in pyruvate dehydrogenase (PDH) activity in response to insulin than those from sedentary controls. Incubation with insulin of liver particulate fractions from exercised group A rats resulted in an increased production of a mitochondrial PDH activator compared with preparations from sedentary controls. The tissues of both exercised and sedentary group B rats were less responsive to insulin than those of the smaller rats. A significant effect of exercise on increased production of a PDH activator in response to insulin was found only in experiments in which adipocyte plasma membranes were coincubated with mitochondria and insulin. For group B rats exercise provided no significant enhancement of insulin activation of intact adipocyte PDH or stimulation of the production of a PDH activator by liver particulate preparations. Insulin binding to fat cells was not affected by exercise. Group A rats made insulin resistant by a high-fat diet did not respond to exercise by significantly increasing the insulin stimulation of PDH activator by liver membranes. The enhancing effect of a single bout of exercise on insulin response was not readily demonstrable in rats resistant to insulin either in association with age and weight or with a high-fat diet.(ABSTRACT TRUNCATED AT 250 WORDS)