Effect of Guanyl Nucleotides on Parathyroid Hormone-Responsive Adenylate Cyclase in Chick Kidney

Hunt, Nicholas H.; Martin, T. J.; Michelangeli, V. P.; Eisman, J. A.

doi:10.1677/joe.0.0690401

Cited by 57 publications

(30 citation statements)

References 11 publications

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“…Only the white-coloured fraction of the resulting pellet was used. The preparations were incubated with [32P]ATP in an ATP-regenerating system of phosphoenolpyruvate and pyruvate kinase as previously described [36]. Time course of binding and dissociation 125I-sCT binding was time-dependent, increasing to a maximum after 4 h at 22°C (Fig.…”

Section: Preparation Of Placental Membrane Fractionmentioning

confidence: 99%

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Human placental calcitonin receptors

Nicholson

D’Santos

Evans

et al. 1988

Biochemical Journal

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Receptors for the hypocalcaemic hormone, calcitonin (CT), have been identified in a membrane fraction prepared from term human placentae. Binding of 125I-labelled salmon CT (125I-sCT) to the membranes was time- and temperature-dependent, saturable (Bmax. 58 +/- 11 fmol/mg of protein), of high affinity (Kd 80 +/- 21 pM) and poorly reversible. Species-specific CTs and CT analogues competed for 125I-sCT binding with potencies proportional to their known biological potencies. Various unrelated peptide hormones did not compete, indicating that receptor binding was specific for CT. Photoaffinity labelling using a derivatized biologically active sCT analogue, [Arg11,18,3-nitrophenylazide-Lys14]sCT, identified a receptor component of Mr approximately 85,000, comparable with findings in osteoclasts and other target cells. The presence of CT receptors in the human placenta supports other evidence that CT may have a role in the regulation of placental function.

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Section: Preparation Of Placental Membrane Fractionmentioning

confidence: 99%

“…Aliquots were incubated with and without 300 nM-sCT in the absence or presence of 100 /SM-GTP or 10 gM-GTPyS. Adenylate cyclase activity was measured as described previously [36].…”

Section: Saturation Analysismentioning

confidence: 99%

Human placental calcitonin receptors

Nicholson

D’Santos

Evans

et al. 1988

Biochemical Journal

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“…PTH receptors are coupled to adenylate cyclase by G proteins in a number of tissues. In renal cortex 35 - 36 and renal microvessels, 29 PTH-stimulated cAMP production is enhanced by G nucleotide analogues. Most studies show PTH to be coupled to adenylate cyclase by G,.…”

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confidence: 97%

Parathyroid hormone/adenylate cyclase coupling in vascular smooth muscle cells.

Hanson

Linas

1994

Hypertension

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Parathyroid hormone (PTH) has been implicated in hypertension, but PTH infusion results in vasodilation. PTH activates adenylate cyclase in vascular smooth muscle, but little is known about the factors that regulate PTH receptor/ adenylate cyclase coupling in vascular cells. To characterize hormone-receptor signaling, we measured cyclic AMP levels in rat arterial smooth muscle cells in culture exposed to PTH (bovine 1-34). PTH yielded time-and concentration-dependent increases in cyclic AMP levels. Compared with isoproterenol, PTH was more potent, with a threshold at 2x10"' versus 5 x 10~8 mol/L and half maximal responses at 10" 8 versus 2.4xlO" 7 mol/L. PTH-induced increases in cyclic AMP were independent of extracellular calcium, cyclooxygenase metabolites, phospholipase C, and protein kinase C because PTHinduced increases in cyclic AMP were not prevented by variations in extracellular calcium, indomethacin, angiotensin II, vasopressin, and protein kinase C activators or inhibitors. PTH/adenylate cyclase coupling was G protein-dependent because increases in cyclic AMP were prevented by preincubation with cholera toxin but not with pertussis toxin. Pro-P arathyroid hormone (PTH) is important in the regulation of calcium, phosphate, and bone metabolism. In addition, PTH has significant effects on vascular tone and has been implicated in the generation and maintenance of high blood pressure. Sustained increases in PTH have been implicated in hypertension, 1 and parathyroidectomy has been found to reverse hypertension in some animal models.2 -3 However, infusion of PTH results in a reduction in blood pressure and vasodilation in several animal models. 46These apparent discrepancies are difficult to resolve in vivo because the primary effects of PTH may be offset by counterregulatory responses that mask hormone action.The cellular effects of PTH are mediated by receptors coupled to adenylate cyclase in nonvascular tissue such as bone. 7 In vascular smooth muscle cells (VSMCs), adenylate cyclase is an important signaling system mediating vasodilation. /3-Adrenergic agonists are major circulating vasodilators in vivo, and /3-adrenergic receptor (/3-AR)/adenylate cyclase coupling has been extensively studied. In addition to /3-AR, PTH is coupled to adenylate cyclase in vascular smooth muscle tissue. Because the in vivo hemodynamic effects of PTH are not clear and PTH appears to be an important regulator of vasodilator adenylate cyclase signaling in vascular smooth muscle tissue, our purpose was to determine factors that regulate PTH receptor/adenylate cyclase coupling in vitro. To accomplish this goal, we compared PTH with isoproterenol, a well-recognized vasodilator and activator of /3-AR and adenylate cyclase. In addition, we used VSMCs in culture to overcome problems inherent in vivo. Methods Cell CultureMesenteric arterial and aortic VSMCs from 8-to 11-weekold male Sprague-Dawley rats (140 to 245 g) were grown in culture using minimum essential medium (MEM) with Earle's salts supplemented with 10% fetal b...

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“…In these tissues PTH stimulates multiple intracellular signals that include cAMP (2)(3)(4)(5)(6), inositol phosphate, and calcium (7)(8)(9)(10)(11)(12)(13) and activates both protein kinases A (14) and C (15). PTHrelated peptide (PTHrP), which has partial homology to PTH (16), causes the syndrome of humoral hypercalcemia of malignancy, probably by activating receptors it shares with PTH (17)(18)(19)(20)(21).…”

mentioning

confidence: 99%