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Basal and postprandial somatostatin-like immunoreactivity (SLI) is elevated in the peripheral venous plasma of chronic alloxan-diabetic dogs. To determine if this hypersomatostatinemia was the consequence of increased somatostatin release from the pancreas, stomach, or both, plasma SLI was measured in the pancreaticoduodenal, antral, and fundic veins and in the inferior vena cava in response to stimulation by a gastric liver test meal, followed by an intragastric HCl load. Basal and postprandial inferior vena caval plasma SLI levels were significantly higher than the control level (P less than 0.05-0.001), confirming earlier findings. Basal pancreatic venous SLI was 780 +/- 45 pg/ml in the diabetic dogs and 493 +/- 65 pg/ml in the controls (P less than 0.02). In response to the liver meal at pH 7, the incremental pancreatic venous SLI level in the diabetic dogs was 1630 +/- 95 pg/ml, and after HCl it rose to 9479 +/- 384 pg/ml compared to 938 +/- 80 and 4677 +/- 192 pg/ml, respectively, in the controls (P less than 0.02 and P less than 0.005). However, antral and fundic venous SLI levels in the diabetic dogs did not differ from the controls in either basal or stimulated states. The present data demonstrate that the pancreas and not the stomach is the probable source of the peripheral hypersomatostatinemia of alloxan-diabetic dogs.

Recent studies have demonstrated that an acidified liver meal stimulates insulin release and raises plasma glucose levels. To examine the mechanism of these changes, a liver extract test meal at either pH7 or at pH2 was instilled into the stomach of dogs with a bisected pylorus and a gastric fistula during the infusion of either cimetidine, a specific H2-receptor antagonist, or a saline control. In response to the meal at pH2 insulin, glucagon and glucose levels rose significantly and were not significantly changed by the infusion of cimetidine. In response to the liver meal at pH7 a late rise in plasma glucagon levels was observed while plasma insulin and glucose did not change significantly; however, during the infusion of cimetidine a significant rise in plasma insulin and glucose levels occurred. The present data suggest that H2-receptors participate in an inhibitory mechanism with respect to the insulin and glucose response during the gastric phase of a neutral meal, but they do not seem to be involved in the rise in insulin and glucose observed in response to an acidified gastric meal.