Calcium-activated proteases in the bovine parathyroid gland: potential role in degradation of parathyroid hormone to peptide fragments

1995 ◽  
Vol 15 (1) ◽  
pp. 61-71 ◽  
Author(s):  
P H Watson ◽  
S T Mortimer ◽  
K K W Wang ◽  
D E Croall ◽  
D A Hanley
Keyword(s):  
Parathyroid Hormone ◽  
Parathyroid Tissue ◽  
Area Under The Curve ◽  
Molar Ratio ◽  
Cell Protein ◽  
Parathyroid Cell ◽  
Peptide Fragments ◽  
Intracellular Degradation ◽  
Peak Areas

ABSTRACT Our studies suggest that protein kinase C is involved in low calcium (Ca2+)-stimulated secretion of parathyroid hormone (PTH) but not directly in high Ca2+-stimulated intracellular degradation of PTH to secreted carboxyl-terminal fragments (C-PTH), an important component of Ca2+-regulated PTH secretion. The present study was undertaken to determine the presence of calciumactivated proteases, 84 kDa (micro)-calpain and 80 kDa (milli)-calpain, in the bovine parathyroid, and whether they could degrade PTH to C-terminal fragments. Immunocytochemistry of bovine parathyroid tissue using antibodies raised against bovine heart micro- and milli-calpain detected both isoforms of calpain. Western blotting of total bovine parathyroid cell protein prepared from primary cell cultures confirmed the presence of both isoforms of calpain, demonstrated by specific milli- and micro-calpain bands. Purified bovine PTH (bPTH) was incubated in vitro with human erythrocyte micro-calpain and the cleavage products were separated by reverse-phase HPLC. Eluant fractions were assayed with an RIA with equimolar sensitivity to C-PTH and bPTH, and peak areas integrated. Micro-calpain produced a C-PTH peak from bPTH which co-eluted with the major C-PTH secreted by parathyroid cells in culture. C-PTH production by micro-calpain, expressed as per cent area under the curve, increased from 0% in the absence of either micro-calpain or Ca2+, to 71·5% when a 5:1 molar ratio of bPTH to calpain was used. Amino acid sequencing and analysis of the immunoreactive PTH cleavage products indicated the presence of two fragments of bPTH in the C-PTH peak, bPTH47–84 and bPTH69–84. In summary, both isoforms of calpain are present in the bovine parathyroid and calpains may play a role in the Ca2+-dependent degradation of PTH to secreted C-terminal fragments.

scholarly journals The release of parathyroid hormone and the exocytosis of a proteoglycan are modulated by extracellular Ca2+ in a similar manner.

1994 ◽  
Vol 5 (7) ◽  
pp. 725-737 ◽  
Author(s):  
Z Muresan ◽  
R R MacGregor
Keyword(s):  
Parathyroid Hormone ◽  
Dermatan Sulfate ◽  
Combined Processes ◽  
Parathyroid Cell ◽  
Intracellular Degradation ◽  
Secretion Pathway ◽  
Dermatan Sulfate Proteoglycan ◽  
Constitutive Secretion ◽  
Intracellular Storage ◽  
Putative Marker

Secretion of parathyroid hormone (PTH) is regulated in part by a classical "stimulus-secretion" pathway responsive to catecholamines. The primary physiological modulator of PTH exocytosis in parathyroid cells, however, is extracellular free Ca2+. Ca(2+)-modulated PTH release exhibits several characteristics suggestive of constitutive secretion. The aim of this work was to obtain further information about the possible intracellular origins of Ca(2+)-modulated exocytosis in parathyroid cells. Freshly dissociated bovine parathyroid cells labeled with [35S]sulfate synthesized a soluble chondroitin/dermatan sulfate proteoglycan (M(r) approximately 90-150 K) that was secreted into the medium. The export of [35S]sulfated proteoglycan satisfied several criteria that generally define constitutive release: 1) export is detected in the medium shortly (7-15 min) after a 5-min pulse, 2) there is minimal intracellular storage after equilibrium labeling (because of combined processes of rapid release and intracellular degradation), and 3) there is insensitivity to stimulation with isoproterenol, a known secretagogue in parathyroid cells. Nevertheless, the increase in extracellular Ca2+ from 0.5 to 2.0 mM reduced the export of the [35S]sulfated proteoglycan from 60% of total labeled to 30%. In addition, a secreted pool of immunoreactive PTH and [35S]sulfated proteoglycan was modulated by external Ca2+ to the same degree and sensitivity, although isoproterenol was more effective in stimulating the release of PTH than that of proteoglycan. Together, our experimental results show that in the parathyroid cell extracellular Ca2+ modulates negatively the export of both PTH and proteoglycan, a putative marker for constitutive secretion. We further suggest that a portion of newly synthesized PTH also enters this pathway, whereas another portion proceeds to an isoproterenol-releasable compartment from which the proteoglycan is largely excluded.

scholarly journals Studies of Interactions of Valsartan, Glimepiride and Ciprofloxacin HCl by DSC and HPLC

2018 ◽  
Vol 20 (2) ◽  
pp. 194-199 ◽  
Author(s):  
Mohammad Farhadur Rahman ◽  
Md Abdus Salam ◽  
Asma Rahman ◽  
Md Zakir Sultan
Keyword(s):  
Pharmaceutical Journal ◽  
Hplc Method ◽  
Molar Ratio ◽  
Percentage Recovery ◽  
Peak Areas ◽  
Melting Endotherm ◽  
In Vitro Interactions

This article deals with the results of in vitro interactions among glimepiride, ciprofloxacin HCl and valsartan at the molar ratio of 1:1:1 by DSC and HPLC method. The DSC thermogram of the mixture (glimepiride, ciprofloxacin HCl and valsartan) showed different melting endotherm than the melting endotherm for standard valsartan, ciprofloxacin HCl and glimepiride. Since the melting endotherms of mixture and individual drugs were not identical, it demonstrated the presence of interactions among the drugs. This result was further verified by HPLC to observe their recovery range. The % recovery ranges were found as 25.33, 23.49 and 135.82% for glimepiride, ciprofloxacin HCl and valsartan, respectively. The abnormal percentage recovery range and peak areas fluctuation further indicated the interactions among glimepiride, ciprofloxacin HCl and valsartan.Bangladesh Pharmaceutical Journal 20(2): 194-199, 2017

Effects of 1,25- and 24,25-dihydroxycholecalciferol on parathyroid hormone release from human parathyroid cells in vitro

1984 ◽  
Vol 105 (3) ◽  
pp. 354-359 ◽  
Author(s):  
Claes Rudberg ◽  
Göran Åkerström ◽  
Henry Johansson ◽  
Sverker Ljunghall ◽  
Jan Malmaeus ◽  
...  
Keyword(s):  
Vitamin D ◽  
Parathyroid Hormone ◽  
Parathyroid Tissue ◽  
Vitamin D Metabolites ◽  
Hormone Release ◽  
High Doses ◽  
Parathyroid Hormone Release ◽  
Dispersed Cells

Abstract. The effects of 125-dihydroxycholecalciferol (1,25-(OH)2D3) and 24,25-dihydroxycholecalciferol (24,25-(OH)2D3) on parathyroid hormone (PTH) release from human parathyroid cells were investigated using an in vitro system of dispersed cells. The cells were obtained from 7 patients with primary hyperparathyroidism (HPT) and adenoma, 4 patients with primary HPT due to hyperplasia and 2 patients with parathyroid hyperplasia secondary to chronic renal failure. The dispersed cells were incubated in tissue culture medium at low, normal and high external calcium concentrations for 2–16 h. There was a gradual suppression of PTH release (5–55%) when the calcium concentration in the medium was increased from 0.5 to 3.0 mM, thus indicating retained regulation of hormone release. The addition of 1,25-(OH)2D3 in concentrations of 0.1 and 1 ng/ml and of 24,25-(OH)2D3 in concentrations of 1.0 and 10 ng/ml during the incubations did not further affect the amount of PTH released by the cells. The concentrations of the different vitamin D metabolites tested closely correspond to levels observed under normal physiological conditions and during treatment with high doses of vitamin D in vivo. Thus, the findings contradict the idea of any direct short-term regulatory effect of either 1,25-(OH)2D3 or 24,25-(OH)2D3 on the secretion of PTH from hyperfunctioning human parathyroid tissue.

Role of hexose monophosphate shunt in parathyroid hormone secretion

1983 ◽  
Vol 245 (5) ◽  
pp. E468-E475 ◽  
Author(s):  
J. J. Morrissey ◽  
S. Klahr
Keyword(s):  
Parathyroid Hormone ◽  
Calcium Ion ◽  
Hormone Secretion ◽  
Parathyroid Tissue ◽  
Ion Concentration ◽  
Cell Protein ◽  
Leucine Incorporation ◽  
Dependent Manner ◽  
Phenazine Methosulfate ◽  
14Co2 Release

The metabolism of labeled glucose by collagenase-dispersed bovine parathyroid cells was examined. When the medium calcium ion concentration was increased to 2.0 mM, the rate of 14CO2 release from [1-14C]glucose was increased 169 +/- 45% compared with the rate of 0.5 mM calcium. There was no significant change in the rate of 14CO2 release from [6-14C]glucose by this maneuver. The greatest increase in 14CO2 release and decrease in parathyroid hormone secretion occurred between medium calcium ion concentrations of 0.5-1.5 mM. This difference in the metabolism of glucose represents a true increase in hexose shunt activity because the incorporation of label from either [1-14C]- or [6-14C]glucose into parathyroid tissue lipids was equal. This suggests equilibration of label at the level of triose-phosphates. The increase in hexose shunt activity was not due to a calcium-mediated increase in glucose uptake because calcium changes did not affect 2-[3H]deoxyglucose transport by the cells. Phenazine methosulfate added to cells incubated at 0.5 mM calcium selectively increased hexose shunt activity in a dose-dependent manner (91 +/- 33% overall) and concomitantly inhibited parathyroid hormone secretion 65% overall at 0.5 mM calcium. The compound 6-aminonicotinamide inhibited hexose shunt activity but could not overcome the inhibition of hormone secretion at 2.0 mM calcium. A decrease in protein biosynthesis cannot fully explain the inhibition of hormone secretion by calcium or phenazine methosulfate because [3H]-leucine incorporation into total cell protein was not as affected as secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Central Venous Sampling for Intraoperative Parathyroid Hormone Monitoring: Are Peripheral Guidelines Applicable?

2007 ◽  
Vol 73 (7) ◽  
pp. 712-716 ◽  
Author(s):  
James T. Broome ◽  
Jason J. Schrager ◽  
Dean Bilheimer ◽  
Eugene P. Chambers ◽  
J. Kenneth Jacobs ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Characteristic Curve ◽  
Parathyroid Tissue ◽  
Area Under The Curve ◽  
Interquartile Range ◽  
Central Venous ◽  
Parathyroid Hormone Monitoring ◽  
Intraoperative Pth ◽  
The Difference ◽  
Intraoperative Parathyroid Hormone

Intraoperative parathyroid hormone (PTH) monitoring has become an integral adjunct to minimally invasive parathyroidectomy. Guidelines for predicting therapeutic excision of all hyperactive parathyroid tissue have been routinely based on peripheral blood samples drawn at various time intervals. Whether these same guidelines can be used to predict success based on central blood draws has not been established. The authors wanted to evaluate whether peripheral criteria were applicable when PTH levels were drawn from a central location. Simultaneous peripheral venous (PV) and central venous (CV) PTH samples were drawn from 64 patients undergoing cervical exploration for primary hyperparathyroidism. Median preexcision PTH was significantly higher centrally at 165 pg/mL (interquartile range [IQR], 101–391 pg/mL) versus peripherally 102 pg/mL (interquartile range, 73–156 pg/mL, P < 0.0001). Postexcision PTH was slightly greater in CV (38 pg/mL; IQR, 24–62) than in PV (29 pg/mL; IQR, 22–51; P < 0.0001). The decrease in intraoperative PTH was compared after excision of an initial gland. Fifty-four of the 64 patients had all hyperfunctioning parathyroid tissue removed after initial gland resection. Pre- to postexcision ratios for CV and PV were compared using receiver operating characteristic curve methods, and summarized by area under the curve (AUC). PV (AUC = 0.85) appears to be a slightly more sensitive discriminator than CV (AUC = 0.83), although the difference is not statistically significant ( P = 0.5). Despite higher absolute values for CV, both peripheral and central sample sites accurately predict outcomes based on established guidelines for intraoperative PTH monitoring.

Parathyroid hormone mRNA levels are increased by progestins and vary during rat estrous cycle

1996 ◽  
Vol 270 (1) ◽  
pp. E158-E163 ◽  
Author(s):  
E. Epstein ◽  
J. Silver ◽  
G. Almogi ◽  
N. Livni ◽  
T. Naveh-Many
Keyword(s):  
Parathyroid Hormone ◽  
Estrous Cycle ◽  
Primary Cultures ◽  
Parathyroid Tissue ◽  
Ovariectomized Rats ◽  
Mrna Levels ◽  
Physiological Relevance ◽  
Weanling Rats

Estrogen increases parathyroid hormone (PTH) mRNA levels in vivo in ovariectomized rats. We now show that the 19-norprogestin R-5020 given to weanling rats or mature ovariectomized rats led to a twofold increase in thyroparathyroid PTH mRNA levels. This increase in PTH mRNA occurred at 24 and 48 h after progesterone but not at 72 h. There were no changes in serum calcium. In vitro, in primary cultures of bovine parathyroid cells, progesterone increased PTH mRNA levels threefold at 10(-8) M and twofold at 10(-9) M after 24 h. Progesterone receptor (PR) mRNA was demonstrated in rat parathyroid tissue by in situ hybridization and in human parathyroid adenoma by immunohisto-chemistry. Changes in PTH mRNA levels during the rat estrous cycle were also studied. At proestrus and estrus PTH mRNA levels were increased significantly by three- and fourfold compared with diestrus. Our results confirm that the parathyroid gland is a target organ for the ovarian sex steroids estrogen and progesterone and are of physiological relevance as shown by the changes during estrus.

Severe Primary Hyperparathyroidism in a Neonate With Two Hypercalcemic Parents: Management With Parathyroidectomy and Heterotopic Autotransplantation

PEDIATRICS ◽  
1986 ◽  
Vol 78 (2) ◽  
pp. 263-268
Author(s):  
Linda Cooper ◽  
Joseph Wertheimer ◽  
Raphael Levey ◽  
Edward Brown ◽  
Meryl Leboff ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Primary Hyperparathyroidism ◽  
Confounding Factor ◽  
Parathyroid Tissue ◽  
Normal Serum ◽  
Familial Hypocalciuric Hypercalcemia ◽  
Normal Range ◽  
Hormone Levels ◽  
Immunoreactive Parathyroid Hormone

A neonate with severe primary hyperparthyroidism was successfully managed by parathyroidectomy and heterotopic autotransplantation (one third of one gland of the infant was implanted in the forearm). In vitro studies of parathyroid tissue from the infant revealed a severe defect in parathyroid suppressibility. Postoperatively, the infant had modest hypercalcemia, normal serum immunoreactive parathyroid hormone levels, hypermagnesemia, and relative hypocalciuria. The parents were related and both had asymptomatic hypercalcemia with mean serum immunoreactive parathyroid hormone levels that were within the normal range. Similar to the findings in the infant postoperatively, relative hypocalciuria in the presence of hypercalcemia was found in the mother; in contrast, the father had hypercalciuria. The presumed dominantly transmitted hypercalcemia in this kindred is consistent with familial hypocalciuric hypercalcemia with a confounding factor of ethanol possibly accounting for the hypercalciuria in the father.

Dopamine-stimulated parathyroid hormone release in vitro: further evidence for a two-pool model of parathyroid hormone secretion

1985 ◽  
Vol 63 (9) ◽  
pp. 1139-1144 ◽  
Author(s):  
David A. Hanley ◽  
Paul G. Wellings
Keyword(s):  
Parathyroid Hormone ◽  
Hormone Secretion ◽  
Parathyroid Tissue ◽  
Hormone Release ◽  
Low Calcium ◽  
Pool Model ◽  
Parathyroid Hormone Release ◽  
Perifusion System ◽  
Sustained Increase

Bovine parathyroid tissue was placed in an in vitro perifusion system for the study of parathyroid hormone secretion stimulated by low calcium and dopamine. Dopamine caused a transient increase in parathyroid hormone release, while low calcium caused a sustained increase in parathyroid hormone secretion. The dopamine response was similar to that caused by isoproterenol. After parathyroid hormone release had been stimulated by dopamine there was no response to isoproterenol, suggesting they cause the release of the same cellular pool of hormone. Inhibition of protein synthesis with cycloheximide eliminated the response to low calcium, with no effect on dopamine-stimulated parathyroid hormone release. These studies suggest dopamine stimulates the release of a limited quantity storage pool of parathyroid hormone, while low calcium causes a sustained release of hormone by stimulating secretion of newly synthesized hormone. Low calcium has little or no effect on release of the storage granule pool of parathyroid hormone.

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