A MOUSE GROWTH HORMONE-BINDING PROTEIN RIA - CONCENTRATIONS IN MATERNAL SERUM DURING PREGNANCY

A RIA for mouse growth hormone-binding protein (mGHBP) was developed. A 28-amino acid synthetic peptide corresponding to the carboxyl-terminal 27 amino acids of mGHBP plus an additional cysteine residue at the amino-terminus was coupled to keyhole limpet hemocyanin and used as the antigen for antiserum production. The ability of the antiserum to recognize mGHBP was demonstrated by incubating mouse serum with I-125-iodomouse GH (mGH) in the presence of increasing concentrations of antiserum and subsequent immunoprecipitation. The antiserum precipitated mGHBP in a dose-dependent manner. The uncoupled synthetic peptide was used as the standard and radioligand in the RIA. Serial dilutions of sera from non-pregnant or 17-days-pregnant mice yielded displacement curves parallel to the synthetic peptide, with serum from 17-days-pregnant mice being 32 times more effective than serum from non-pregnant mice for a given dilution. The relative concentration of mGHBP in maternal serum on days 5, 11, and 15 of pregnancy was 1, 17, and 39, respectively.