Immunological comparisons of two synthetic human parathyroid hormone-(1-34) peptides

The immunological properties of human parathyroid hormone-)1-34) synthesized in accord with the sequence reported by Brewer et al. and the different sequence found by Niall et al. were compared with those of highly purified native human hormone-)1-84). Analyses were performed by radioimmunoassay using 7 anti-bovine parathyroid hormone antisera and bovine parathyroid hormone-)1-34) as tracer. Whereas human parathyroid hormone-(1-34) synthesized in accord with the sequence of Niall et al. was immunologically indistinguishable from native human hormone in all 7 assay systems, striking differences were seen between human parathyroid hormone-(1-34) synthesized in accord with the sequence of Brewer et al. and the native hormone. In none of the 7 assay systems did human parathyroid hormone-(1-34) synthesized in accord with the sequence of Brewer et al. give the same displacement slopes that the reference preparation gave. The observation that immunologic probes easily discriminate between the two different human parathyroid hormone-(1-34) peptides suggests that similar immunologic approaches will be of value in exploring several important issues, particularly those relating to the sequence and conformational properties of human parathyroid hormone and its synthetic peptides and to the question of the existence of isohormonal forms.