Evidence for a hypophyseal factor that stimulates insulin secretion by the pancreas (insulotrophine?).

The continuous infusion of glucose (1 mg/kg/min) via the carotid artery in anesthetized dogs produced a biphasic pattern of insulin secretion. The first peak reached a maximum 3 min after glucose infusion and decreased to basal level at 7 min. As long as glucose infusion persisted a slow and maintained increase in insulin level in the pancreatico-duodenal vein was observed. The same amount of glucose infused in to the carotid arteries of hypophysectomized dogs, failed to induce any change in plasma insulin level. Plasma sample obtained from the jugular vein of dogs receiving glucose via the carotid arteries were infused into a second dog via the pancreatico-duodenal artery. One minute after the onset of infusion a rise in insulin was observed in the pancreatico-duodenal vein. The stimulating effect was not due to the high blood glucose level present in the jugular vein of dogs undergoing the cephalic glucose infusion. Infusion through the pancreatico-duodenal artery of a glucose solution at a concentration equal to the highest blood glucose level observed in the jugular vein did not evoke insulin secretion. Plasma samples obtained from the jugular vein of dogs receiving saline via the carotid arteries did not evoke insulin secretion when receiving into the pancreatico-duodenal arteries of dogs. Pancreatic infusion of plasma obtained from the jugular vein of hypophysectomized dogs infused glucose through the carotid arteries did not evoke any pancreatic response. These findings are demonstrative of the presence of a hypophyseal humoral insulin stimulating factor in the jugular vein of dogs receiving a cephalic glucose load.