Characterization of a high-affinity antiserum specific for the amino-terminal sequence of human parathyroid hormone

RESUMO

1. The present paper describes a detailed study of the specificity of high-affinitu antibodies obtained from the yolk of eggs laid by achicken successfully immunized with synthetic human parathyroid hormone (hPTH)-(1-34). 2. Using 125I-labelled bovine parathyroide hormone (bPTH)-(1-84) puridied by high performance liquid chromatography (HPLC) as tracer, and hPTH-(1-34) as reference, we found superimposable curves with hPTH-(13-34), bPTH-(13-34) and bTH-(1-34); the [Asp-76]hPTH-(1-84) peptide showed a molar percent cross-reactivity (calculated at 50% B/BO) of 73% and the bovine sequence 1-84 of 15%. 3. Studying amidated [Tyr-34] bovine PTH fragments we found the highest cross-reactivity with the peptide 7-34 (1.7%) and 25-34 (0.4%). The bovine sequence 1-25 showed a low reactivity (0.7%) and the 1-12 sequence none at all . Rat parathyroid hormone (rPTH)- (1-34) showed low cross-reactivity (3.1%), the same occuring with peptide [Tyr-34, Norleu-8,18]bPTH-(1-34) (1.5%). 4. The data suggest that the antibodies studied recognize epitopes in or near amino acids 18 to 25 of the sequence of the hPTH molecule. This region of the molecule is coincident with the antigenic determinant predicted by the abalysis of the hydrophilicity plot of the hPTH-(1-34) peptide