The effects of insulin on the utilization of propionate in glucose synthesis were studied in fed and fasted sheep. Insulin was infused at 0.04 μ/h into the mesenteric vein. Glucose was infused to prevent hypoglycaemia. The rate of incorporation of [2-14C]propionate into glucose was determined before and during insulin infusion. After 150 min of insulin infusion endogenous glucose synthesis was about 70% of control values, whereas the incorporation of [14C]propionate into plasma glucose was 94% of control values. In contrast, the incorporation of other glucose precursors into glucose was decreased 30–50% by insulin. Therefore, insulin does not appear to decrease the utilization of propionate in gluconeogenesis. These results are consistent with the proposition that insulin differentially affects the rate of incorporation of glucose precursors into glucose in ruminant animals.
