Development of a Radioimmunoassay for Plasma C-Peptide in Sheep: Kinetics of C-Peptide and Effects of Exogenous Growth Hormone and Glucose on Insulin and C-Peptide

Abstract

An antiserum to purified bovine C-peptide was used to develop a sensitive radioimmunoassay for C-peptide in sheep. The assay was used to measure kinetics of C-peptide and insulin in non-pregnant and non-lactating sheep. Injected, purified C-peptide was distributed in pools comprising c. 11·4% of liveweight, the half time of C-peptide was estimated as 13·7 min and its clearance rate was c. 5 ml kg-I min-I. In lactating ewes exogenous recombinant bovine growth hormone (rebGH) increased both plasma insulin and C-peptide as did glucose challenge given before and during administration of rebGH. Estimates of insulin secretion rate in lactating ewes were c. 7 X 10-3 and 8·5 x 10-3 nmol kg-I min-I before and after glucose challenge prior to injections of rebGH. After 4 days of injection of rebGH, corresponding values were c. 8 x 10- 3 and 10 x 10-3 nmol min-I kg-I.