In vitro perifusion for the study of parathyroid hormone secretion: Effects of extracellular calcium concentration and beta-adrenergic regulation on bovine parathyroid hormone secretion in vitro

Hanley, David A.; Takatsuki, K; Birnbaumer, Mariel; Schneider, Arthur B.; Sherwood, Louis M.

doi:10.1007/bf02408518

Cited by 42 publications

(20 citation statements)

References 33 publications

(58 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although adaptive mechanisms have evolved to control the amount of Ca 2þ that is absorbed, the efficiency of this response involves metabolic changes, whose persistence with time may be deleterious. 21 reabsorption (14) . This is an adaptation process performed as a compensation mechanism in order to cover the cation needs of the organism (15) .…”

Section: Introductionmentioning

confidence: 99%

Molecular mechanisms triggered by low-calcium diets

et al. 2009

View full text Add to dashboard Cite

Ca is not only essential for bone mineralisation, but also for regulation of extracellular and intracellular processes. When the Ca2+ intake is low, the efficiency of intestinal Ca2+ absorption and renal Ca2+ reabsorption is increased. This adaptive mechanism involves calcitriol enhancement via parathyroid hormone stimulation. Bone is also highly affected. Low Ca2+ intake is considered a risk factor for osteoporosis. Patients with renal lithiasis may be at higher risk of recurrence of stone formation when they have low Ca2+ intake. The role of dietary Ca2+ on the regulation of lipid metabolism and lipogenic genes in adipocytes might explain an inverse relationship between dairy intake and BMI. Dietary Ca2+ restriction produces impairment of the adipocyte apoptosis and dysregulation of glucocorticosteroid metabolism in the adipose tissue. An inverse relationship between hypertension and a low-Ca2+ diet has been described. Ca2+ facilitates weight loss and stimulates insulin sensitivity, which contributes to the decrease in the blood pressure. There is also evidence that dietary Ca2+ is associated with colorectal cancer. Dietary Ca2+ could alter the ratio of faecal bile acids, reducing the cytotoxicity of faecal water, or it could activate Ca2+-sensing receptors, triggering intracellular signalling pathways. Also it could bind luminal antigens, transporting them into mucosal mononuclear cells as a mechanism of immunosurveillance and promotion of tolerance. Data relative to nutritional Ca2+ and incidences of other human cancers are controversial. Health professionals should be aware of these nutritional complications and reinforce the dairy intakes to ensure the recommended Ca2+ requirements and prevent diseases.

show abstract

Section: Introductionmentioning

confidence: 99%

Molecular mechanisms triggered by low-calcium diets

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Parathyroid hormone (PTH) and 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) are the principal hormones regulating calcium homeostasis (1)(2)(3). Both (4)(5)(6)(7)(8).…”

mentioning

confidence: 99%

“…Moreover, after administration of 1,25-(OH)2[3H]D3 to chicks and rats, there is marked accumulation of the metabolite in the parathyroid glands, particularly in the nuclei (13,14). Vitamin (1).…”

mentioning

confidence: 99%

Regulation by vitamin D metabolites of messenger ribonucleic acid for preproparathyroid hormone in isolated bovine parathyroid cells.

Silver¹,

Russell²,

Sherwood³

1985

Proc. Natl. Acad. Sci. U.S.A.

456

154

View full text Add to dashboard Cite

We have recently determined that high calcium concentrations, in parallel with their suppressive effects on parathyroid hormone (PTH) secretion, reversibly and specifically decrease preproPTH mRNA in cultured bovine parathyroid cells. In order to determine whether vitamin D metabolites also regulate the content of preproPTH mRNA, we tested their effects on bovine parathyroid cells in the same culture system. Levels of preproPTH mRNA were determined by dot-blot hybridization or blot hybridization with a labeled cloned cDNA probe. Incubation with 1,25-dihydroxycholecalciferol at doses varying from 10 pM to 0.1 jiM caused a direct decrease in mRNA down to 50% of control values at 48 hr.There was no evidence that 1,25-dihydroxycholecalciferol, even at the highest concentrations, had any toxic effects on cell number or viability or on total RNA or RNA synthesis. Eagle's medium containing 1.25 mM Ca2+, 10% fetal calf serum, and 1% penicillin and streptomycin. Prior to incubation, cell number and viability were determined by direct cell count with a hemocytometer and by Trypan blue dye exclusion, respectively.Bovine parathyroid cells were maintained in primary monolayer culture for 24-72 hr, at which time old medium was removed and replaced with fresh medium containing either one of the vitamin D metabolites to be tested or vehicle (10 ,ul of ethanol) alone. Each set of conditions was carried out in quadruplicate. At the end of each experiment, cell number and viability were determined as described above after removing the cells with trypsin/EDTA (GIBCO). In addition, cells cultured for 48 hr were tested for their ability to respond acutely to high and low calcium by incubation with fresh medium containing bovine serum albumin at 2 mg/ml; 1.0 mM magnesium; 0.5, 1.25, or 2.5 mM calcium; and no 1,25-(OH)2D3 at 37°C for 30 min. Medium was then removed for radioimmunoassay of PTH (1).Extraction of Total RNA. At different time intervals, the medium was aspirated, cells were removed and washed, and total cellular RNA was extracted with guanidine thiocyanate by the method of Ulrich et al. (15). Total RNA was redissolved in sterile water and quantitated by reading the absorbancy at 260 nm. The absorbancy at 280 nm also was determined, and the ratio of A26w/A280 in all cases was between 1.9-2.0.In some cases the cells were pulsed with [3H]uridine (10 ,uCi/ml of medium; 1 Ci = 37 GBq) for 6 hr prior to extraction of RNA as described above. Unincorporated label was removed by two successive precipitations with 2.5 vol of ethanol in the presence of 0.3 M sodium acetate (pH 5.2).Abbreviations: PTH, parathyroid hormone; D3, cholecalciferol; 1,25-(OH)2D3, 1,25-dihydroxycholecalciferol; 24,25-(OH)2D3, 24,25-dihydroxycholecalciferol; 25-OH-D3, 25-hydroxycholecalciferol. 4270The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

show abstract

“…On the other hand, extracellular calcium is well established as an inhibitor of PITH release (1). Possibly then, regulation by calcium at the level of the plasma membrane, rather than the cytoplasm, identifies the parathyroid as a uniquely controlled cell.…”

Section: Resultsmentioning

confidence: 99%

“…Physiologic control of parathyroid hormone (PTH) secretion is regulated by changes in extracellular calcium, with low concentrations of calcium stimulating and high concentrations of calcium inhibiting hormone release (1)(2)(3)(4). How extracellular changes in calcium levels are recognized by the parathyroid cell and what transduces signal recognition into intracellular processes controlling exocytosis and PTH secretion are as yet uncertain.…”

Section: Introductionmentioning

confidence: 99%

Regulation of protein kinase C by extracellular calcium in bovine parathyroid cells.

Kobayashi

Russell

Lettieri

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Regulation of protein kinase C in the parathyroid gland was investigated by testing the effects of phorbol ester, exogenous phospholipase C, and low and high calcium concentrations on enzyme activity. Treatment of bovine parathyroid cells with phorbol ester, which activates protein kinase C directly, and with phospholipase C, which produces diacylglycerol, an activator of protein kinase C, significantly stimulated protein kinase C activity. Both agents also enhanced the release of parathyroid hormone. Acute exposure of bovine parathyroid cells to low extracellular calcium (0.5 mM) caused a 5-to 6-fold increase in protein kinase C activity associated with the particulate fraction. In contrast, high extracellular calcium (1.75 mM and 2.5 mM) markedly decreased membrane protein kinase C activity. These data suggest that the effects of extraceilular calcium on parathyroid hormone secretion are due, at least in part, to regulation of protein kinase C activity in the parathyroid-cell membrane.Physiologic control of parathyroid hormone (PTH) secretion is regulated by changes in extracellular calcium, with low concentrations of calcium stimulating and high concentrations of calcium inhibiting hormone release (1-4). How extracellular changes in calcium levels are recognized by the parathyroid cell and what transduces signal recognition into intracellular processes controlling exocytosis and PTH secretion are as yet uncertain.Recent studies suggest that protein kinase C, which is activated by calcium, phospholipid, and diacylglycerol, plays an important role in exocytosis (5). Therefore, we examined the role of protein kinase C in regulation by extracellular calcium of PTH secretion by testing the effects of phorbol ester, exogenous phospholipase C (PLC), and low and high calcium concentrations on protein kinase C activity in isolated bovine parathyroid cells.This Dispersed parathyroid cells were prepared by collagenase digestion of minced glands (6). After purification on Percoll gradients, the cells (which equilibrated within a buoyant density of 1.048-1.062) were aspirated, washed, and resuspended in basal Eagle's medium (BME). Protein kinase C activity was measured by a modification of the method of Kikkawa et al. (7). After cells were lysed and sonicated with 3 ml of buffer A (20 mM Tris HCI, pH 7.5, containing 0.25 M sucrose, 10 mM EGTA, and 2 mM EDTA), cytosolic and particulate membrane fractions were prepared by centrifugation at 100,000 x g for 60 min. The centrifuged membrane pellet was homogenized with a glass rod in 1% Nonidet P-40 buffer A. Crude extracts from the membrane and cytosolic fractions were applied to a 1-ml DE-52 column equilibrated with buffer B (20 mM Tris-HCI, pH 7.5, containing 50 mM 2-mercaptoethanol, 5 mM EGTA, and 2 mM EDTA). Columns were washed with 15 ml of buffer B, 15 ml of buffer C (20 mM Tris-HCI, pH 7.5, containing 50 mM 2-mercaptoethanol, 1 mM EGTA, and 1 mM EDTA), and 0.5 ml of buffer C containing 0.1 M NaCl. An additional 1.5 ml of 0.1 M NaCl/buffer C eluate was then colle...

show abstract

In vitro perifusion for the study of parathyroid hormone secretion: Effects of extracellular calcium concentration and beta-adrenergic regulation on bovine parathyroid hormone secretion in vitro

Cited by 42 publications

References 33 publications

Molecular mechanisms triggered by low-calcium diets

Molecular mechanisms triggered by low-calcium diets

Regulation by vitamin D metabolites of messenger ribonucleic acid for preproparathyroid hormone in isolated bovine parathyroid cells.

Regulation of protein kinase C by extracellular calcium in bovine parathyroid cells.

Contact Info

Product

Resources

About