Radioimmunoassay for porcine lipotrophic peptide B.

A sensitive radioimmunoassay for the lipolytic peptide B from pig pituitary glands has been developed. Antisera were raised in rabbits, which allowed a final dilution of 1:6000. Free and antibody bound [125I]peptide B could be separated by double antibody, by dextran-coated charcoal and by polyethyleneglycol. The smallest detectable amount was 0.5 ng/ml. Peptide B could be measured irregularly in porcine sera; there was cross-reacting material in an extract of a total human pituitary gland, but not in human sera. The assay seems specific except for a strong cross-reaction with porcine neurophysin. There are indications that peptide B consists of neurophysin and a small lipolytically active peptide which remains to be further characterized.