Investigations on insulin kinetics

Insulin is secreted into the portal vein by the pancreas at varying rates. The insulin secretion rate is calculated by deconvolution from C-peptide concentrations, a peptide that is co-secreted with insulin on an equimolar basis. This calculation has been experimentally validated. It is concluded that, in dogs, as portal insulin levels increase to 600uU/ml, the hepatic extraction of insulin falls by approximately 50% and the fractional disappearance rate of insulin by two thirds. This suggests that insulin removal by the liver is the principal component of the metabolic clearance of insulin and that it may vary under physiological circumstances. This paper provides approaches, both experimental and quantitative for determining the major parameters involved in insulin kinetics - its rate of secretion and removal by the liver, when these are varying.