The Limitations to and Valid Use of C-Peptide as a Marker of the Secretion of Insulin

作者：K. S. Polonsky, B. Frank, William C. Pugh, Antonio Addis, Theodore G Karrison, Petra Sylvia Meier, Howard S. Tager, Arthur H. Rubenstein · 发表于：Diabetes · 年份：1986 · DOI：10.2337/diab.35.4.379 · 被引用次数：111 · 研究领域：Pancreatic function and diabetes、Diabetes and associated disorders、Diabetes Management and Research

The accuracy with which the secretion rate of insulin can be calculated from peripheral concentrations of C-peptide was investigated in conscious mongrel dogs. Biosynthetic human C-peptide and insulin were infused intraportally and their concentrations measured in the femoral artery. During steady-state infusions of C-peptide, the peripheral concentration changed in proportion to the infusion rate and the metabolic clearance rate (5.2 ± 0.3 ml/kg/min) remained constant over a wide range of plasma concentrations. Application of a two-compartment mathematical model, in which the model parameters were estimated from analysis of C-peptide decay curves after intravenous bolus injections, allowed the intraportal infusion rate of C-peptide to be derived from peripheral C-peptide concentrations, even under non-steady-state conditions. Estimates of the intraportal infusion rate based on this model were 102.4 ± 2.6% of the actual infusion rate as it was increasing and 102.3 ± 5.5% of this rate as it was falling. The peripheral C-peptide : insulin molar ratio was influenced by the rate at which equimolar intraportal infusions of C-peptide and insulin were changed. The baseline C-peptide : insulin molar ratio (4.1 ± 0.9) increased to peak values of 8.2 ± 0.6,10.3 ± 2.0, and 14.9 ±1.3 when the infusion rate was increased and then decreased rapidly. Peak values of only 5.7 ±1.2 were found if the intraportal infusion rate was changed slowly. In conclusion: (1) under steady-state conditions ...