[Effect of somatostatin on pancreatic endocrine--experiment by somatostatin infusion into the pancreaticoduodenal artery in dogs--(author's transl)].

The direct inhibitory action of somatostatin (cyclized SRIF) on the pancreatic endocrine function was investigated by a technique using pancreaticoduodenal arteriovenous system in vivo. Somatostatin was infused for 20 minutes at a speed of 2.5 mug/minute into the superior pancreaticoduodenal vein and femoral artery were measured before and every 5 minutes throughout the experiment for 30 minutes. The results were compared with those obtained from the control experiment which was carried out in the same time schedule under infusion of physiologic saline solution instead of somatostatin. Next, the effect of somatostatin on the glucose-induced insulin release from the pancreas was also evaluated. The following findings were obtained. (1) Somatostatin infused at a speed of 2.5 mug/minute into the superior pancreaticoduodenal artery caused a statistically significant inhibition of plasma levels of IRI and IRG and also pancreatic output of these hormones. With the sessation of somatostatin infusion an abrupt rise of the hormones were seen. This "rebound" phenomenon was more pronounced in insulin secretion than in glucagon. No significant changes in the plasma glucose levels in either the pancreaticoduodenal vein or the femoral artery throughout the experiment were found. (2)During infusion of somatostatin at a speed of 1.25 mug/minute, insulin response to glucose injected into the pancreaticoduodenal artery in a small dose, as well as having no effect on the plasma glucose level in systemic circulation, was also significantly inhibited. From these findings obtained by direct experiment using the pancreaticoduodenal arterio-venous system, it was confirmed that somatostatin exhibits a direct inhibitory action on pancreas endocrine in a very low concentration in vivo, and it was suggested that this action might be partly due to a reduction in pancreatic circulation.