Identification and purification of parathyroid hypertensive factor from organ culture of parathyroid glands from spontaneously hypertensive rats.

Parathyroid hypertensive factor (PHF) is a newly described hypertensive factor isolated from the plasma of spontaneously hypertensive rats (SHR). Recent studies have suggested that the primary origin of PHF is the parathyroid gland (PG). In the present investigation, PG from spontaneously hypertensive rats (SHR), as well as from normotensive rats, were isolated and maintained in culture. The PG from SHR, but not normotensive rats, released PHF into the culture medium. Omission of calcium from the culture medium stimulated the release of PHF. For purification of PHF, parathyroid gland culture medium (PGCM) was first dialyzed at 1000 mwco, and then ultrafiltered at 5000 molecular weight cut-off (mwco). PHF activity was retained in the fraction that was greater than 1000 daltons and less than 5000 daltons. Dialyzed and filtered SHR PGCM was fractionated by molecular exclusion HPLC. Biologically active PHF was collected in a discrete region. The biologically active molecular exclusion fraction was subsequently fractionated by reverse-phase HPLC (C-8). PHF was collected in a single discrete peak, which did not occur in culture medium prepared from normotensive PG in a similar manner. This biologically active peak occurred in the same position on molecular exclusion and reverse-phase HPLC as PHF purified from SHR plasma using similar procedures. Incubation of PGCM with trypsin inactivates the biological activity of PHF. The UV spectrum of PGCM PHF is identical to that obtained from purified plasma PHF. These results are consistent with the presence of a peptide moiety in PHF, and support the parathyroid origin of plasma PHF.