Preliminary evidence for a microsomal precursor to human parathyroid hormone.

Human parathyroid glands from a patient with chronic renal failure were used to study in vitro biosynthesis of immunoreactive parathyroid hormone. Parathyroid glands were incubated in the presence of [(3)H]leucine, and classical subcellular fractions were prepared. peptides from acetic acid extractions of the fractions were separated on Sephadex G-75 Superfine. Eluates were assayed for immunoreactive parathyroid hormone by a double-antibody technique. Leucine was incorporated into several large immunoreactive peptides of parathyroid hormone having estimated molecular weights of >25,000, 18,000, and 13,000. The large forms of immunoreactive parathyroid hormone were prominant in the microsomes. The secretion granule fraction, as well as the patient's serum, contained principally immunoreactive parathyroid hormone with an apparent molecular weight of 10,000.