Portal venous injection of insulin in the diabetic rat: time of induction of changes in hepatic lipogenesis, cholesterogenesis, and glycogenesis

Abstract

The time of onset of changes in liver metabolism of the 14-hour-insulin-deprived, alloxan-diabetic rat following continuous portal vein infusion of insulin was studied. The earliest effect of insulin—on glycogen content of the liver and on the capacity of the liver slice to synthesize cholesterol from acetate—occurred between 10 and 30 minutes after the start of the infusion. The liver's capacity for incorporating acetate carbon into cholesterol rose dramatically between 30 and 60 minutes after the start of the hormone infusion, and returned to normal in 90 minutes. The significance of this biphasic response in hepatic cholesterogenesis to portal vein insulin infusion is discussed. Fatty acid synthesis was slowest to respond to insulin. An effect on hepatic lipogenesis was first detected between 60 and 90 minutes after injection, and the liver's capacity for incorporation of acetate-l-C14 into fatty acids continued to increase with duration of insulin administration up to 180 minutes.