A specific anti-proinsulin serum and the presence of proinsulin in calf serum.

A specific antibody against proinsulin has been obtained by adsorbing the original anti-proinsulin guinea pig serum with a solid immunosorbent of Sephadex-insulin. The specificity of the antibody against antigenic determinants of proinsulin was established by radioimmunoassay and by passive cutaneous anaphylaxis (PCA) tests. The presence of proinsulin in calf serum has been demonstrated by (a) gel filtration of an acid alcohol extract of the serum followed by immunoassays of the fractions using anti-insulin or the specific anti-proinsulin serum, and (b) direct assay of calf serum with the specific anti-proinsulin serum.