scholarly journals Secretion and degradation of parathormone as a function of intracellular maturation of hormone pools

1979 ◽  
Vol 83 (3) ◽  
pp. 521-528 ◽  
Author(s):  
JJ Morrissey ◽  
DV Cohn
Keyword(s):  
Cyclic Amp ◽  
Half Life ◽  
Calcium Concentration ◽  
Hormone Secretion ◽  
Ionized Calcium ◽  
Dibutyryl Cyclic Amp ◽  
Low Calcium ◽  
High Calcium ◽  
Parathormone Secretion

The biosynthesis, processing, and secretion of parthormone and the effect of calcium on these processes were measured in dispersed porcine parthyroid cells incubated with [(35)S]methionine. Proparathormone was detected at 10 min, the earliest time measured, and was rapidly and apparently quantitatively converted to parathormone. The half-life of the prohomormone pool was 15 min. Secretion of parathormone was detected by 20 min. In pulse-chase experiments there was a period between 20 and 40 min during which the wave of newly-synthesized parathormone was secreted. After 40 min during little additional radioactive hormone was secreted, but dibutyryl cyclic AMP, an agent that can mobilize stored parathormone, when added to the incubation mixtures enhanced radioactive parathormone secretion but only after 60 min, although it increased net hormone secretion as determined by radioimmunoassay to the same extent at all times studied. When the ionized calcium concentration of the medium was lowered, more radioactive hormone was secreted at all times but the effect was greatest on that hormone that was synthesized less than 60 min previously ; however, net hormone secretion in contrast to radioactive hormone was enhanced equally at all intervals. These data could mean that the refractoriness to secretion of parathormone 40-60 min of age was related to maturation of secretory container preparatory to storage. Low calcium (0.5 mM) stimulated hormone secretion up to fivefold compared to high calcium (3.0 mM) but did not affect synthesis of parathormone or proparathormne or conversion of the latter to hormone. During processing at least 70 percent of the intracellular parathormone was lost, presumably through proteolysis and this degradation was greater at high calcium. These data have been interpreted in light of the concept that two secretable pools of parathormone exist within the parathyroid.

Involvement of glutathione oxidation reduction in parathyroid hormone secretion

1986 ◽  
Vol 250 (4) ◽  
pp. E475-E479
Author(s):  
J. J. Morrissey
Keyword(s):  
Calcium Concentration ◽  
Reduced Glutathione ◽  
Hormone Secretion ◽  
Cellular Protein ◽  
Cell Protein ◽  
Glutathione Metabolism ◽  
Low Calcium ◽  
Oxidation Reduction ◽  
High Calcium ◽  
Glutathione Oxidation

This study determines whether calcium affects glutathione metabolism and whether glutathione metabolism may influence parathyroid (PTH) secretion in collagenase dispersed bovine parathyroid cells. Reduced glutathione (GSH) and glutathione disulfide (GSSG) were measured fluorometrically and enzymatically while PTH secretion was determined by radioimmunoassay. The total GSH and GSSG content of parathyroid cells was found to range from 1.59 to 1.71 micrograms/mg cell protein, and this did not vary significantly with changes in extracellular calcium. An increase in the medium calcium concentration from 0.5 to 2.0 mM did, however, cause an increase in GSSG from 0.43-0.54 to 1.19-1.20 micrograms/mg protein with a concomitant decrease in GSH. The compound 2-cyclohexen-1-one was used to deplete the cells of GSH at a low-calcium medium (0.5 mM) to levels seen in high-calcium medium (2.0 mM). This treatment was found to inhibit PTH secretion in the low-calcium medium, as if the cells were incubated in high medium calcium. Both 2-cyclohexen-1-one and calcium caused a rapid decrease in reduced GSH levels and in hormone secretion. The ketone was not found to affect cellular protein synthesis, indicating that there was no nonspecific toxic effect of this treatment on the cells. These results suggest that changes in the calcium concentration of the medium affect the GSH/GSSG ratio of dispersed parathyroid cells. Changes in the GSH/GSSG ratio induced by calcium may be related to changes in PTH secretion.

scholarly journals Calcium metabolism and cardiovascular function after spaceflight

2002 ◽  
Vol 92 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Daniel C. Hatton ◽  
Qi Yue ◽  
Jacqueline Dierickx ◽  
Chantal Roullet ◽  
Keiichi Otsuka ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Calcium Metabolism ◽  
Calcium Concentration ◽  
Dietary Calcium ◽  
Ionized Calcium ◽  
Free Calcium ◽  
Mineral Density ◽  
Spontaneously Hypertensive ◽  
Low Calcium ◽  
High Calcium

To determine the influence of dietary calcium on spaceflight-induced alterations in calcium metabolism and blood pressure (BP), 9-wk-old spontaneously hypertensive rats, fed either high- (2%) or low-calcium (0.02%) diets, were flown on an 18-day shuttle flight. On landing, flight animals had increased ionized calcium ( P < 0.001), elevated parathyroid hormone levels ( P < 0.001), reduced calcitonin levels ( P < 0.05), unchanged 1,25(OH)2D3levels, and elevated skull ( P < 0.01) and reduced femur bone mineral density. Basal and thrombin-stimulated platelet free calcium (intracellular calcium concentration) were also reduced ( P < 0.05). There was a tendency for indirect systolic BP to be reduced in conscious flight animals ( P = 0.057). However, mean arterial pressure was elevated ( P < 0.001) after anesthesia. Dietary calcium altered all aspects of calcium metabolism ( P < 0.001), as well as BP ( P < 0.001), but the only interaction with flight was a relatively greater increase in ionized calcium in flight animals fed low- compared with high-calcium diets ( P < 0.05). The results indicate that 1) flight-induced disruptions of calcium metabolism are relatively impervious to dietary calcium in the short term, 2) increased ionized calcium did not normalize low-calcium-induced elevations of BP, and 3) parathyroid hormone was paradoxically increased in the high-calcium-fed flight animals after landing.

scholarly journals Regulation of secretion of parathormone and secretory protein-I from separate intracellular pools by calcium, dibutyryl cyclic AMP, and (1)-isoproterenol.

1979 ◽  
Vol 82 (1) ◽  
pp. 93-102 ◽  
Author(s):  
J J Morrissey ◽  
D V Cohn
Keyword(s):  
Amino Acids ◽  
Cyclic Amp ◽  
Calcium Concentration ◽  
Hormone Secretion ◽  
Specific Radioactivity ◽  
Secretory Protein ◽  
Parathyroid Cell ◽  
Dibutyryl Cyclic Amp ◽  
Intracellular Pool ◽  
Enhanced Secretion

Dispersed porcine parathyroid cells were incubated at calcium concentrations between 0.5 and 3.0 mM in the presence of 3H- or 14C-amino acids to label newly synthesized parathormone. Up to four times more hormone was secreted at the lower calcium concentration but its specific radioactivity, from 30 to 50 times that of the intracellular pool, did not change. Dibutyrl cyclic AMP doubled immunoactive parathormone secretion at each calcium concentration, but there was no increase in secretion of radioactive hormone if labeled amino acids and secretagogue were added simultaneously. Similarly, when the intracellular pool of parathormone was prelabeled with 3H-amino acids and then the cells were incubated in 14C-amino acids and dibutyryl cyclic AMP, the entire increase in hormone secreted was derived from the prelabeled pool. (1)-isoproterenol increased intracellular cyclic AMP and acted on hormone secretion in a manner indistinguishable from dibutyryl cyclic AMP. In similar double-label experiments dibutyryl cyclic AMP preferentially enhanced secretion of secretory protein-I, a calcium-regulated protein of the parathyroid of unknown function. Calcium, alone, inhibited the intracellular level of cyclic AMP in a concentration-dependent fashion. These data are consistent with the existence in the parathyroid cell preparation of two hormone and secretory protein pools that may be individually recruitable--one consisting of most recently synthesized protein, the other consisting of older "storage" protein. The data do not allow one to decide whether the two pools coexist within individual cells or whether, instead, they exist in separate cells of the dispersed gland preparation.

Effect of phorbol myristate acetate on secretion of parathyroid hormone

1988 ◽  
Vol 254 (1) ◽  
pp. E63-E70 ◽  
Author(s):  
J. J. Morrissey
Keyword(s):  
Protein Kinase C ◽  
Parathyroid Hormone ◽  
Protein Kinase ◽  
Membrane Fraction ◽  
Hormone Secretion ◽  
Myristate Acetate ◽  
Kinase C ◽  
Low Calcium ◽  
Protein Kinase C Activity ◽  
High Calcium

The influence of phorbol myristate acetate (PMA), an activator of protein kinase c, on the secretion of parathyroid hormone from collagenase-dispersed bovine parathyroid cells was tested. The cells were incubated at low (0.5 mM) or high (2.0 mM) concentrations of calcium in the medium, and the hormone secreted into the medium was measured by a radioimmunoassay that recognizes both intact and C-terminal fragments of hormone. At low calcium, the secretory rate averaged 32 +/- 3.8 ng.h-1.(10(5) cells)-1. The addition of 1.6 microM PMA did not affect secretion. At high calcium there was a significant suppression of secretion by 38% to 19.8 +/- 3 ng.h-1.(10(5) cells)-1. The addition of 1.6 microM PMA significantly stimulated hormone secretion to 35.8 +/- 8 ng.h-1.(10(5) cells)-1, a rate indistinguishable from low calcium. This stimulatory effect of PMA at high calcium was seen at PMA concentrations as low as 1.6 nM, did not occur with a biologically inactive 4 alpha-isomer of phorbol ester, and was independent of changes in cellular adenosine 3',5'-cyclic monophosphate levels. Examination of 32P-labeled phosphoproteins by two-dimensional gel electrophoresis revealed acidic proteins of approximately 20,000 and 100,000 Da that were phosphorylated at low and high calcium + 1.6 microM PMA but not at high calcium alone. The protein kinase c activity associated with the membrane fraction of parathyroid cells significantly decreased 40% when the cells were incubated at high vs. low calcium. The data suggest that calcium may regulate parathyroid hormone secretion through changes in protein kinase c activity of the membrane fraction of the cell and protein phosphorylation.

scholarly journals Magnesium modulates parathyroid hormone secretion and upregulates parathyroid receptor expression at moderately low calcium concentration

2013 ◽  
Vol 29 (2) ◽  
pp. 282-289 ◽  
Author(s):  
M. E. Rodriguez-Ortiz ◽  
A. Canalejo ◽  
C. Herencia ◽  
J. M. Martinez-Moreno ◽  
A. Peralta-Ramirez ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Calcium Concentration ◽  
Hormone Secretion ◽  
Receptor Expression ◽  
Low Calcium

scholarly journals The regulation of growth hormone secretion from the isolated rat anterior pituitary in vitro. The role of adenosine 3′:5′-cyclic monophosphate

1971 ◽  
Vol 124 (4) ◽  
pp. 815-826 ◽  
Author(s):  
R. B. Lockhart Ewart ◽  
K. W. Taylor
Keyword(s):  
Growth Hormone ◽  
Cyclic Amp ◽  
Early Phase ◽  
Late Phase ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Hormone Release ◽  
Dibutyryl Cyclic Amp ◽  
Cyclic Monophosphate

1. The release of growth hormone from isolated fragments of rat anterior pituitary tissue incubated in vitro was studied by employing a double-antibody radioimmunoassay. 2. In the absence of added stimuli, two phases of hormone release could be distinguished, an early phase of 2h duration and a subsequent late phase. In the early phase, hormone release was rapid but could be significantly decreased by calcium depletion and by 2,4-dinitrophenol whereas the rate of release in the late phase was uninfluenced by these incubation conditions. These results have been interpreted as indicating the existence of a secretory component in the early phase of release. 3. In subsequent experiments, the effects of various agents on the rate of hormone output during the late phase of incubation were investigated. Hormone release was increased by theophylline and by dibutyryl cyclic AMP (N6-2′-O-dibutyryl-adenosine 3′:5′-cyclic monophosphate), the response to both of these agents being related to the concentration of the stimulant employed. 4. The stimulation of growth hormone output by theophylline was significantly decreased by calcium deprivation and by 2,4-dinitrophenol. The response to dibutyryl cyclic AMP was diminished by 2,4-dinitrophenol, iodoacetate and 2-deoxyglucose but not by malonate or colchicine. 5. Arginine, β-hydroxybutyrate, albumin-bound palmitate and variation in the glucose concentration of the incubation medium over a wide range were without any statistically significant effect on the rate of hormone release from either control pituitary fragments or those subject to secretory stimulation by dibutyryl cyclic AMP. 6. It is suggested that the regulation of growth hormone secretion is mediated by cyclic AMP (adenosine 3′:5′-cyclic monophosphate). The secretion observed in response to cyclic AMP requires the presence of ionized calcium and a source of metabolic energy but is independent of pituitary protein synthesis de novo. The integrity of the glycolytic pathway of glucose metabolism appears to be essential for cyclic AMP-stimulated growth hormone secretion to occur.

scholarly journals ADP-induced platelet shape change and mobilization of cytoplasmic ionized calcium are mediated by distinct binding sites on platelets: 5'- p-fluorosulfonylbenzoyladenosine is a weak platelet agonist

Blood ◽  
1987 ◽  
Vol 70 (3) ◽  
pp. 751-756 ◽  
Author(s):  
AK Rao ◽  
MA Kowalska
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Binding Sites ◽  
Calcium Concentration ◽  
Shape Change ◽  
Ionized Calcium ◽  
Platelet Binding ◽  
Thiol Reagent ◽  
Dose Dependent ◽  
Platelet Shape

Abstract Platelet stimulation with ADP results in several responses, including shape change, increase in cytoplasmic ionized calcium concentration [Ca2+]i, an inhibition of adenylate cyclase. 5′-p-Fluorosulphonyl benzoyladenosine (FSBA), which covalently labels an ADP binding site on platelets, blocks platelet shape change but not the inhibition of cyclic AMP levels by ADP, whereas p-chloromercuribenzenesulfonate (pCMBS), a nonpenetrating thiol reagent, has the opposite effects. We examined the effect of FSBA and pCMBS on ADP-induced increase in [Ca2+]i using platelets loaded with fluorescent Ca2+ indicators quin2 and fura-2. FSBA (50 to 200 mumol/L) induced a dose-dependent rise in [Ca2+]i, indicating that it is a weak platelet agonist. Under conditions of covalent labeling of the ADP binding sites, FSBA (50 to 100 mumol/L) did not inhibit the ADP-induced increase in [Ca2+]i or its inhibition of adenylate cyclase, whereas pCMBS (up to 1 mmol/L) abolished both these responses but not shape change. These findings suggest that ADP-induced Ca2+ mobilization and inhibition of adenylate cyclase are mediated by platelet binding sites distinct from those mediating shape change.

Ambient pH and Calcium Concentration as Modifiers of Growth and Calcium Dynamics of Brook Trout, Salvelinus fontinalis

1984 ◽  
Vol 41 (12) ◽  
pp. 1774-1780 ◽  
Author(s):  
David W. Rodgers
Keyword(s):  
Brook Trout ◽  
Calcium Concentration ◽  
Salvelinus Fontinalis ◽  
Axial Skeleton ◽  
Low Ph ◽  
Fish Growth ◽  
Calcium Dynamics ◽  
Experimental Fish ◽  
Low Calcium ◽  
High Calcium

Juvenile brook trout, Salvelinus fontinalis, were maintained in water of pH 5.3 or 6.5 and calcium concentrations of 5 or 40 mg/L to determine the effects of these factors on fish growth and calcium dynamics. Growth rates varied more than twofold and were significantly reduced by both low ambient calcium concentration and low pH. In contrast, calcium dynamics of the fish were significantly affected by calcium concentration but not pH. Brook trout in low-calcium water retained less labeled dietary calcium and deposited less labeled calcium in axial skeleton and visceral tissues than fish in high-calcium water. Calcium concentrations of the skin and fins were slightly but significantly reduced among fish in low-calcium water, but neither pH nor ambient calcium concentration significantly affected ash content or calcium concentration of axial skeleton and visceral tissues of experimental fish.

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