Attempts to immunoprecipitate the LHRH precursor synthesized in cell free systems

In order to determine the molecular weight of the Luteinizing Hormone Releasing Hormone (LHRH) precursor, poly(A)-RNA from rat hypothalami and human placenta were translated in two mRNA dependent cell free translation systems. Total translation products were immunoprecipitated with two antisera that recognized LHRH high molecular weight forms. After SDS-polyacrylamide slab gel electrophoretic analysis of the immunoprecipitated material and fluorography, we detected in both tissues a protein of 50,000 daltons with the No. 1076 antiserum. This peptide was not immunoprecipitated by the No. 743 anti-LHRH antiserum or by non-immune rabbit serum. However, this protein was not displaced by excess LHRH added during the immunoprecipitation and seemed to be present in species where LHRH has not been reported. These data demonstrated that the LHRH mRNA is present in very low amounts in hypothalamus or placenta and that the sensitivity of the assay is not high enough to recognize it.