Changes in gut and liver glucose, lactate, insulin, and oxygen flux in mature ewes during mesenteric or abdominal vena cava glucose infusion.

The objective of the study was to determine whether exogenous glucose infusion affects endogenous glucose production in ewes. Mature ewes with catheters placed in the abdominal aorta, two mesenteric veins, the hepatic portal vein and the hepatic vein were used to determine the effect of exogenous glucose infusion on net glucose, insulin, lactate and oxygen flux by the portal-drained viscera (PDV) and liver of conscious sheep. Net hepatic glucose release was determined, and glucose was subsequently infused into either a mesenteric vein or an abdominal vena cava at an equal rate (mmol/L) for 240 min, and net fluxes were determined every 30 min. Arterial concentrations of glucose and insulin increased over time, whereas lactate concentration decreased over time (P < 0.05). Hepatic glucose release decreased linearly over time when glucose was infused into the mesenteric vein (P = 0.03) and tended to decrease linearly when glucose was infused into the abdominal vena cava (P = 0.06). Net PDV and splanchnic plasma insulin release during the vena cava infusion increased linearly over time (P < 0.02). Net PDV blood lactate release did not differ between infusion sites (P = 0.75), nor did the release rate change over time (P > 0.10). Net splanchnic lactate release in the abdominal vena++ cava infusion, however, did decrease over time (P = 0.05). Net hepatic oxygen consumption decreased quadratically over time (P = 0.004) when glucose was infused into the mesenteric vein. In conclusion, infusion of glucose results in a decrease in hepatic glucose production.