ISOLATION AND CHARACTERIZATION OF THE BIOACTIVE CIRCULATING HUMAN PARATHYROID-HORMONE, HPTH-1-37

The occurrence of hPTH-1-37 as the native bioactive circulating form o f PTH-1-84 has now been obtained using a specific purification procedu re for circulating parathyroid hormone, which involves a newly develop ed immunoenzymetric assay for N-terminally intact hPTH. In combination with two different methods of mass spectrometry, the molecular weight of the isolated immunoreactive peptide was shown to be 4401 Da, which corresponds to hPTH-1-37. Synthetic hPTH-1-37 material was tested in the chick bioassay and produced a clear-cut increase in serum calcium concentration, We conclude that hPTH-1-37 is the native bioactive frag ment of hPTH-1-84 in circulation.