Plasma insulin responses to glucose in femoral, hepatic, and pancreatic veins in dogs

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Abstract
Responses of plasma insulin to intravenous administration of glucose (I g/kg) in the femoral, hepatic, and superior pancreaticoduodenal veins were studied by frequent blood samplings in anesthetized dogs. Blood samples of the hepatic and the pancreaticoduodenal veins were taken by catheterization. Injection of glucose produced a prompt increase in plasma insulin in all 3 veins as measured by radioimmunoassay, but the change in peripheral vein insulin was not a simple reflection of that of the pancreatic vein. Insulin responses were more variable than glucose tolerance curves, and very often there were additional peaks in insulin curve besides the initial peak. These secondary peaks were clearly observed in pancreatic vein in virtually all cases, but they were less prominent or even absent in other veins. Comparison of 2 groups classified according to their glucose tolerance revealed that secondary peaks in insulin response tended to be delayed and exaggerated when glucose tolerance was depressed. The discrepancy between insulin curved of different veins and the significance of secondary peaks are discussed.