Acute hormonal regulation of gluconeogenesis in isolated rainbow trout hepatocytes

Gluconeogenesis from lactate in hepatocytes from rainbow trout was activated by glucagon and inhibited by insulin in a dose-dependent fashion. The maximal responses to both hormones occurred within their probable physiological concentration ranges. Gluconeogenic activation by glucagon was accompanied by a profound inhibition of pyruvate kinase activity. This was reflected in increases in both the So.o and nH for phosphoenolpyruvate and increased sensitivity to inhibition by MgATP compared to the enzyme isolated from cells not treated with hormone (control). Gluconeogenic inhibition by insulin was accompanied by activation of pyruvate kinase activity. This was reflected in decreases in both the So.o and nH for phosphoenolpyruvate and a decreased sensitivity to inhibition by MgATP compared to enzyme isolated from control cells. This contrasts with previous suggestions that these pancreatic hormones are not important in the regulation of carbohydrate metabolism in fishes.Science, Faculty ofZoology, Department ofGraduat