Advances in the treatment of clinical disorders of mineral in homeostatis and metabolic bone disease with intact parathyroid hormone 1-84 or one of the biologically active N-terminal fragments require a precise and sensitive measurement in serum. Therefore, a two-site immunoenzymometric assay for the quantitative determination of bioactive hPTH-1-37 (human parathyroid hormone) at picomolar concentrations was developed. Monoclonal antibodies (mAB) against hPTH-1-37 were raised by hybridoma cells in serum-free cell culture. Furthermore, sequence-specific polyclonal antibodies were obtained by immunisation of rabbits using multiple antigenic peptides (MAP) representing the conspicuous regions of the primary structure of hPTH-1-37. The polyclonal and monoclonal antibodies were characterised by epitope mapping. The combination of a monoclonal antibody (13C63/5) recognising hPTH fragment 16-24 with a polyclonal antibody (k2) showing a predominant binding sequence at hPTH-1-5 led to a sandwich assay specific for N-terminally intact and therefore biologically active hPTH. The validated assay ranging from 4 to 1000 pmol/l was applied to pharmacokinetic studies of hPTH-1-37. After s.c. administration of 30 mu g/kg in 5 beagles, the maximum serum concentrations of hPTH-1-37 ranging at 2139 +/- 857 pmol/l were observed 45 min after the injection. Clearance of the peptide calculated from the exponential disappearance curve was 32.0 +/- 9.1 ml/min/kg with a mean t1/2 of 37 +/- 10 min.
Amino Acid Sequence Animals