Studies on the Pituitary "Fettstoffwechselhormon" - VIII. Radioimmunoassay of the Lipolytic Factor P-LF II D

Abstract

A radioimmunoassay of the lipolytic peptide P-LF II D from porcine pituitaries is described. The assay is performed with 125-iodine labeled P-LF II D and with antisera either from guinea pigs or from rabbits. Bound antigen is separated from the free by double antibody technique. No cross reaction is observed with gamma lipotropin, peptide B, secretin, glucagon, isoproterenol. Due to contamination P-LF II C, beta lipotropin and human growth hormone displace the tracer when added at large doses. Complete cross reaction is observed between porcine 1-39 ACTH and P-LF II D. Specificity of this reaction is demonstrated by the increase of cross reaction, when ACTH fragments of increasing length of the polypeptide chain are used (1-23 ACTH, 1-24 ACTH and 1-28 ACTH).