Substances Immunologically Related to Proinsulin or Connecting Peptide in Swine Plasma

Abstract

A radioimmunoassay that measures both procine proinsulin and the connecting peptide (linking the A and B chains of insulin in the proinsulin molecule) has been used to evaluate the presence of these substances in the plasma of miniature swine. Significant amounts of substances cross-reacting in this assay appeared in the plasma following oral glucose and intravenous glucose, glucagon and tolbutamide. Although the present studies do not distinguish between the relative contributions of proinsulin or connecting peptide, they suggest that biosynthetic precursors of insulin are secreted from the pancreas under similar conditions that stimulate insulin secretion.