Synthesis and secretion of parathyroid hormone in vitro

Degradation of parathyroid hormone and fragment production by the isolated perfused dog kidney. The effect of glomerular filtration rate and perfusate CA++ concentrations.

“…The liver (7,8) and kidney have been shown to produce PTH fragments and to degrade all of the intact hormone added to these isolated organ perfusion circuits within a short time. These studies do not exclude the possibility that circulating PTH fragments in vivo can originate from direct secretion by the parathyroid glands as suggested by other authors (6,17,18). They do suggest that significant fractions of the circulating fragment pool may result from degradation of intact hormone by the kidney.…”

Heterogeneity of Parathyroid Hormone. CLINICAL AND PHYSIOLOGIC IMPLICATIONS

“…is immunochemically distinct from the 9,500 mol wt form of PTH present in parathyroid tissue, and is cleaved from this larger, glandular hormone within the parathyroid gland itself. Sherwood et al (4) reached similar conclusions, estimating the molecular weight of the secreted form to be about 7,000. In contrast, Habener et al (5) reported from in vivo studies that the secreted form of human PTH (hPTH) has a molecular weight of about 9,500, is identical in size and immunochemical behavior to the hormone extractable from glandular tissue, and that cleavage of the secreted species into one or more immunologically heterogeneous fragments occurs peripherally, after its release from the gland.…”

“…When parathyroid glandular extracts have been subjected to gel filtration some investigators (4) have reported that the eluted immunoreactive PTH emerged as a single peak, while others have observed size heterogeneity (2, 7). More recently, use of the pulse-chase technique has established the existence of a prohormonal precursor with a molecular weight of about 12,000 both for bovine (8,9) and for human (10) PTH.…”

Ultrastructural localization of phosphatases in the rat parathyroid gland.

“…Therefore, our results indicated that there was either no ACPase activity in these structures or the activity was below the level of sensitivity of the methods applied. As it has been suggested from a biochemical study in vitro that secretory granules in the parathyroid may be depolimerized from protein molecules into smaller polypeptide molecules before they are released from the cell body (SHERWOOD et al, 1971), further experimental studies may be needed to elucidate whether the ACPase activity is involved in the secretory mechanism or the control mechanism of this gland, or in both.…”