IMMUNOLOGICAL STUDIES ON PARATHYROID HORMONE: CHARACTERIZATION OF ANTISERA AGAINST SYNTHETIC 1–34 HUMAN PARATHYROID HORMONE AND EVIDENCE THAT POSITION 30 IN HUMAN PARATHYROID HORMONE IS ASPARTIC ACID

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Abstract
SUMMARY: Radioimmunoassays for the measurement of the 1–34 human parathyroid hormone fragment (1–34 hPTH) were developed using antisera raised in rabbits against synthetic 1–34 hPTH-N (amino acid sequence proposed by Niall). Binding of 125I-labelled 1–34 hPTH-N to these antisera was optimal at pH 5·5. Limits of detection varied between 25 and 200 pg/ml. Cross-reactivity of 1–34 bovine PTH was substantial in all assays; 1–34 hPTH-B (structure proposed by Brewer), 1–84 hPTH and 1–29 hPTH cross-reacted only with antisera from one animal. 1–29 Human PTH was obtained from partial hydrolysis of both 1–84 hPTH and 1–34 hPTH-N. Production of 1–29 hPTH from 1–84 hPTH was demonstrated by comparison of the elution profiles of the reaction product and 1–29 bovine PTH on Sephadex G-50. Thus, evidence was obtained that position 30 in native hPTH is occupied by an aspartic acid residue.