Insulin in portal, hepatic and peripheral venous blood after glucose, tolbutamide and glipizide stimulation. Indication of insulin release from peripheral tissues.

Insulin in portal, hepatic and/or peripheral venous blood was determined in 16 patients admitted to a surgical ward for various diseases. Portal venous blood was obtained via a catheter introduced into the portal vein either through the umbilical vein remnant or transhepatically. Four subjects were given a peroral load of glucose, followed after 60 min by i.v. tolbutamide. In simultaneous blood samples, two of these subjects showed higher insulin concentrations in peripheral venous blood than in portal venous blood. Twelve subjects were given i.v. glipizide. In one subject blood samples were drawn from the portal vein, a hepatic vein and a peripheral vein and in six subjects from the portal vein and a hepatic vein. Two subjects showed higher insulin concentrations in peripheral venous blood than in portal venous blood. The mean peripheral insulin response (six subjects) was of the same magnitude as the mean hepatic insulin response (six subjects). It is suggested that these findings reflect a release of previously bound insulin from peripheral tissues.