Disappearance of insulin in man: variation with the plasma insulin level
Tranberg, K.G.; Hagander, P.; Thorell, J.
Acta Endocrinologica 97(3): 391-397
1981
ISSN/ISBN: 0001-5598 PMID: 7020317 Document Number: 172780
Clearance rates of unlabeled insulin were studied in 45 unanesthetized non-diabetic humans. The clearance rate, as well as the pancreatic secretion rate, of endogenous insulin was estimated from steady-state concentrations in portal and arterial blood. The clearance rate of exogenous insulin was determined after brief intraportal infusion. In the basal fasting state, the endogenous plasma insulin level varied as closely with the clearance of endogenous insulin as with the rate of pancreatic secretion. During elevation of insulin by glucose infusion, it varied predominantly with the rate of insulin secretion. Clearance of exogenous insulin did not vary with the pre-test endogenous insulin level. The clearance of endogenous insulin increased from 11 ml .cntdot. min-1 .cntdot. kg-1 in the basal fasting state to 17 ml .cntdot. min-1 .cntdot. kg-1 during glucose infusion. Clearance of exogenous insulin fell progressively with increasing dose, from 35 (8 mU/kg) to 14 (43 mU/kg) ml .cntdot. min-1 .cntdot. kg-1 at normoglycemia and from 23 (8 mU/kg) to 17 (34 mU/kg) ml .cntdot. min-1 .cntdot. kg-1 at hyperglycemia. The clearance of endogenous insulin was lower than that of exogenous insulin at normoglycemia, but of similar size during glucose infusion. Variation in clearance rate is partly responsible for variation in plasma insulin concentration, particularly in the basal fasting state, and that the clearance rate is lower in the basal state than otherwise. To some extent, the low clearance values for endogenous insulin in the basal state may reflect poor specificity of the insulin radioimmunoassay.