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Query: UNIPROT:P01185 (vasopressin)
 23,126 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium has been implicated as a regulatory factor in many physiological and pathophysiological processes in the renal cell. Under physiological conditions, the cytosolic free calcium concentration is maintained at approximately 100 nM. Most of the releasable cell Ca2+ resides in the nonmitochondrial compartments. In addition to the plasma membrane Ca2+ transport processes, there is a high-affinity, low-capacity buffering capability of nonmitochondrial organelles and a lower-affinity high-capacity mitochondrial Ca2+ buffering capability. A critical enzymatic effector of Ca2+ action in the cell is phospholipase A2. By using digitonin-permeabilized renal mesangial cells, the [Ca2+] dependency of phospholipase A2 was characterized. The [Ca2+] sensitivity was insufficient to explain the phospholipase A2 activation observed with vasopressin. In both intact cells, as well as permeabilized cells, it was found that protein kinase C activation markedly enhanced the Ca2+ calmodulin-dependent activation of phospholipase A2. In response to platelet-derived growth factor, it was found that arachidonic acid release preceded phospholipase C activation. This suggests that other effectors besides Ca2+ and protein kinase C may also be important for phospholipase A2 activation. In an experimental model designed to mimic postischemic reperfusion damage to renal mitochondria, it was demonstrated that reactive oxygen species act synergistically with Ca2+ to activate mitochondrial phospholipase A2, which mediates damage to site I of the electron transport chain, the F1F0 ATPase, and the adenine nucleotide translocase.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Calcium in renal cells. Modulation of calcium-dependent activation of phospholipase A2. 219 Aug 10

Freshly isolated rabbit proximal tubules (PT), confluent primary rabbit proximal tubule cultures (PTC) and LLC-PK1 cells were characterised. Brushborder enzyme activities were lower in PTC than in LLC-PK1: ratios were 0.026 for alkaline phosphatase (AP), 0.458 for alanine aminopeptidase (AAP) and 0.514 for gamma-glutamyl transpeptidase (GGT). PT/PTC ratios were 79.7 for AP, 7.96 for AAP and 3.45 for GGT. Specific activities of hexokinase (HK) and lactate dehydrogenase (LDH) were high in cultured cells as compared to PT: PT/PTC ratios were 0.063 and 0.033, while PTC/LLC-PK1 ratios were 0.406 and 1.19 for HK and LDH respectively. PTC/LLC-PK1 ratios were 2.21 for Na/K ATPase, 2.07 for succinate dehydrogenase, 1.12 for cathepsin B, 0.607 for N-acetyl-beta-D-glucosaminidase and 8.98 for glutathione-S-transferase. Adenylate cyclase response to parathormone (PTH), was similar in PTC and PT, but stimulated/basal ratios were higher in PT than in PTC. LLC-PK1 cells were stimulated by thyrocalcitonin (SCT), arginin-vasopressin (AVP) and PTH; stimulated/basal ratios ranked AVP greater than PTH greater than SCT. Differences between both types of cultures affect the choice of in vitro model for nephrotoxicity studies.
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PMID:Adenylate cyclase responses and biochemical characterization of primary rabbit proximal tubular cell cultures and LLC-PK1 cells. 228 70

Isolated hepatocytes and the isolated perfused rat liver have been used to study the alterations of cytosolic free Ca2+ concentration ([Ca2+]i) produced by 2,5-di(tert-butyl)-1,4-benzohydroquinone (tBuBHQ), a potent inhibitor of hepatic microsomal Ca2+ sequestration (Moore, G.A., McConkey, D.J., Kass, G.E.N., O'Brien, P.J. and Orrenius, S. FEBS Lett., 224, 331-336), (1987). Addition of tBuBHQ to isolated hepatocytes caused a rapid increase in [Ca2+]i which was similar in magnitude to the [Ca2+]i elevation induced by the Ca2+ mobilizing hormone, vasopressin. In contrast with vasopressin which caused a Ca2+ transient, tBuBHQ elevated [Ca2+]i to a new steady state that was maintained for up to 15-20 min. When vasopressin was administered during the tBuBHQ-induced period of elevated [Ca2+]i, [Ca2+]i rapidly returned to basal levels. Similarly, if vasopressin was administered just prior to tBuBHQ, the resultant tBuBHQ-dependent change in [Ca2+]i was transient, and not sustained. The hydroquinone mobilized the same intracellular Ca2+ pool as inositol 1,4,5-trisphosphate, but tBuBHQ did not produce any detectable inositol polyphosphate accumulation. tBuBHQ stimulated glucose release from perifused hepatocytes, mimicking the effect of vasopressin. In the perfused liver, tBuBHQ infusion produced a single, slow and prolonged release of Ca2+ into the perfusate and inhibition of subsequent vasopressin-induced Ca2+ effluxes. Inhibition of the response to vasopressin was reversed over time, and closely correlated with the extent of inhibition of both Ca2+ sequestration and (Ca2+-Mg2+)-ATPase activity in microsomes isolated from the isolated perfused liver.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:2,5-Di(tert-butyl)-1,4-benzohydroquinone--a novel mobilizer of the inositol 1,4,5-trisphosphate-sensitive Ca2+ pool. 235 9

The liver plasma membrane Ca2+ pump is supposed to extrude cytosolic calcium out of the cell. This system has now been well defined on the basis of its plasma membrane origin, its high affinity Ca2+ -stimulated ATPase activity, its Ca2+ transport activity, its phosphorylated intermediate. The liver calcium pump appears to be a target of hormonal action since it has been shown that glucagon and calcium mobilizing hormones namely alpha 1-adrenergic agonists, vasopressin, angiotensin II inhibit this system. The present review details the mechanism of calcium pump inhibition by glucagon and points out its difference from the inhibition process induced by calcium mobilizing hormones. We conclude that the inhibitory action of the Ca2+ mobilizing hormones and glucagon on the liver plasma membrane Ca2+ pump might play a key role in the actions of these hormones by prolonging the elevation in cytosolic free Ca2+.
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PMID:The liver plasma membrane Ca2+ pump: hormonal sensitivity. 241 53

Human polycystic kidney disease (PKD) epithelia were successfully grown in culture and expressed abnormal characteristics. Cysts lining epithelia of superficial and deep cysts were microdissected and compared to individual normal human proximal straight tubules (PST) and cortical collecting tubules (CCT) grown in defined media. PKD cyst epithelia differed from normal renal tubular epithelia in growth patterns and structural and functional properties. PKD epithelia grew more rapidly and showed cyst-like areas in otherwise confluent monolayers. Polygonal and elongate cells contained an epithelial-specific cytokeratin antigen and had polarized morphology. An extremely abnormal basement membrane morphology was seen and consisted of some banded collagen and numerous unique blebs or spheroids. These blebs were apparently extruded from intracellular vacuoles and stained with ruthenium red, suggesting a proteoglycan component. Cytochemistry of marker enzymes demonstrated the presence of NaK-ATPase and alkaline phosphatase, but a lack of gamma-glutamyl transpeptidase. The response of adenylate cyclase activity to vasopressin, parathyroid hormone, and forskolin was significantly diminished in PKD cells as compared to PST and CCT. These studies suggest a defect in cell growth and basement membrane synthesis in human PKD. Cultured PKD epithelia provide a new tool for the study of the pathogenesis of this disease.
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PMID:A new method for studying human polycystic kidney disease epithelia in culture. 243 Nov 89

Anatagonists to angiotensin, catecholamines, aldosterone, and vasopressin have long been used to help determine agonist roles in hypertension. We here call attention to a possible extension of this approach to detect, evaluate, and treat vascular sodium transport defects in hypertension. Two basic types of transport defects have been identified in the blood vessels of hypertensive animals, increased sodium permeability and decreased sodium pump activity. Intravenous injection of 6-iodo-amiloride, a sodium channel blocker and vasodilator, produces an immediate and sustained decrease in blood pressure in two genetic models of hypertension characterized by increased permeability of the vascular smooth muscle cell membrane to sodium (Okamoto spontaneously hypertensive rat, Dahl salt sensitive rat), whereas it produces only a transient fall in arterial pressure in two renal models of hypertension having normal sodium permeability in vascular smooth muscle cells (reduced renal mass-saline rat, one-kidney, one clip rat). Canrenone, a metabolic product of spironolactone which can compete with oubain for binding to Na+,K+-ATPase at the digitalis receptor site, decreases blood pressure in a low renin, volume expanded model of hypertension which has been shown to have depressed sodium pump activity in arteries and increased sodium pump inhibitor in plasma (reduced renal mass-saline rat) but has no effect on blood pressure in a genetic model of hypertension which has been shown to have increased sodium pump activity secondary to increased sodium permeability (spontaneously hypertensive rat). Thus, a sodium channel blocker and a competitor to ouabain binding can detect and determine the functional significance of sodium transport defects in the blood vessels of intact hypertensive animals. Studies in red and white blood cells suggest that similar defects may exist in the blood vessels of hypertensive humans. Thus, this approach, probing for vascular transport defects in the intact animal, may ultimately also be useful in the clinical setting.
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PMID:Pharmacologic agents for the in vivo detection of vascular sodium transport defects in hypertension. 244 62

Intracellular sodium has been implicated in a variety of cellular processes including regulation of Na+-K+-ATPase activity, mitogen-induced cell growth, and proliferation and stimulation of Na+-K+-ATPase by aldosterone. In renal epithelial cells a rise in sodium uptake across the apical membrane increases intracellular sodium concentration, which in turn stimulates the turnover rate of Na+-K+-ATPase and thereby enhances sodium efflux across the basolateral membrane. A prolonged increase in sodium uptake causes dramatic hypertrophy and hyperplasia and a rise in the quantity of Na+-K+-ATPase in the basolateral membrane. These structural and functional changes occur in the kidney in the absence of alterations in plasma aldosterone and vasopressin levels. Several mitogens induce growth and proliferation by initiating a cascade of events, which include a rise in intracellular sodium. Accordingly, an increase in the sodium concentration within renal epithelial cells may elicit a "mitogen-like" effect by initiating the cascade at the sodium step, even in the absence of a mitogen. A rise in cell sodium may also stimulate the production of autocrine growth factors that directly or indirectly regulate cell growth and proliferation, by modifying the response to mitogens or to changes in the ionic composition of the extracellular fluid. In this review we will examine the evidence that supports a role for intracellular sodium in regulating these cellular events in renal epithelial cells.
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PMID:Regulation of renal ion transport and cell growth by sodium. 254 43

Continuous membrane voltage (V) recordings were obtained in A10 vascular smooth muscle cells (rat aorta) using glass microelectrodes. Resting membrane voltage in 262 impalements averaged 54.0 +/- 0.4 (SE) mV. Relative K+ conductance was characterized, and the contribution of electrogenic Na+-K+-ATPase to membrane voltage was investigated. Action potentials could be induced by application of 1 mM barium or 10(-4) M acetylcholine. In a few recordings, spontaneous spike activity occurred, and this could be abolished by 5 mM MgCl2 or by removal of extracellular Ca2+. Barium-induced action potentials were not dependent on the presence of extracellular Na+ and not inhibitable by 10(-6) M tetrodotoxin. Application of 10(-6) M [Arg8] vasopressin (AVP) for 30 s caused a typical biphasic membrane voltage response with an initial transient hyperpolarization of -9.5 +/- 1.1 mV and a more sustained subsequent depolarizing response averaging 28.2 +/- 1.3 mV (mean +/- SE, n = 58). The effect of AVP on membrane voltage was blocked by the V1-antagonist [beta-mercapto-beta,beta-cyclopentamethylenepropionyl1,O-Me- Tyr2,Arg8]vasopressin. The initial hyperpolarizing component of the membrane voltage response to AVP became more prominent when V was predepolarized, for example, by a preceding AVP application. However, when AVP was applied during high K+ depolarization or in the presence of quinidine (1 mM), the initial hyperpolarizing response was practically abolished. The time course of the initial hyperpolarization was shown to be similar to the calcium transient observed in fura-2-loaded A10 cell suspensions after the application of AVP. We conclude that the initial AVP-induced hyperpolarization in A10 cells corresponds to an activation of Ca2+-activated K+ channels.
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PMID:Continuous membrane voltage recordings in A10 vascular smooth muscle cells: effect of AVP. 254 89

The effects of endothelin on cellular Ca2+ mobilization were examined in cultured rat vascular smooth muscle cells (VSMC). Endothelin (10(-8)M) induced a rapid transient increase of [Ca2+]i from 77 +/- 3 to 104 +/- 5 nM (p less than .05) in VSMC. Preincubation (60 min) with endothelin (2 x 10(-6)M) increased basal [Ca2+]i from 77 +/- 3 to 105 +/- 8 nM (p less than .05). Preincubation with endothelin also enhanced vasopressin (10(-7)M)-stimulated peak levels of [Ca2+]i (528 +/- 20 nM vs 969 +/- 21 nM, p less than .01). Endothelin (10(-7)M) induced an intracellular alkalinization (7.18 +/- 0.03 vs 7.37 +/- 0.04, p less than .01) which was blocked by pretreatment with amiloride. The biphasic effects of endothelin on [Ca2+]i were similar to those of an endogenous inhibitor of Na-K-ATPase that we examined in a previous study. Therefore, we examined the effects of endothelin on Na-K-ATPase in an enzyme preparation from hog cerebral cortex. At high concentrations, endothelin (10(-5)M) inhibited Na-K-ATPase in vitro. Thus, endothelin may exert its vasoconstrictor effects at least in part via alterations of cellular Ca2+ mobilization in VSMC. While the rapid transient increase of [Ca2+]i appears to reflect intracellular Ca2+ mobilization, the sustained effect on [Ca2+]i may be related to an increase of intracellular sodium mediated by inhibition of Na-K-ATPase and/or more likely by stimulation of the Na+/H+-antiport.
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PMID:Effects of endothelin on sodium transport mechanisms: potential role in cellular Ca2+ mobilization. 254 95

Heterogeneity in Madin-Darby canine kidney (MDCK) epithelial cells has been reported, however, its details have not been well described. In the present study, we show that subclones obtained from a MDCK cell line could be divided into two morphologically and biochemically distinct cell types with different hormonal responsiveness. Clones of the first type, motile clones, which had extended and flattened cytoplasm, were devoid of carbonic anhydrase activity. Clones of the second type, nonmotile clones, formed colonies of cuboidal cells and showed carbonic anhydrase activity. Motile clones synthesized cAMP in response to arginine vasopressin, prostaglandin E1, and isoproterenol but not glucagon. In contrast, nonmotile clones responded to all of these hormones. These findings suggest MDCK cells have multiple cellular origins. The motile clones have characteristics similar to the principal cells of the collecting system, whereas the nonmotile clones may be derived from the thick ascending limb or the intercalated cell. Our studies also demonstrate a significant influence of culture condition on MDCK cellular behavior (carbonic anhydrase activity, Na+/K+-ATPase activity and vasopressin responsiveness). Therefore, physiologic and biochemical experiments with MDCK cells must be interpreted with reservations about cellular heterogeneity as well as differences induced by culture conditions.
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PMID:Characterization of subclones of Madin-Darby canine kidney renal epithelial cell line. 255 8


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