Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A sequential mechanism for endothelium-dependent vasorelaxation is proposed. The following events appear to be involved: Endothelial cell: activation of a receptor----activation of membrane phospholipases----increase in intracellular free Ca2+----formation of endothelium-derived relaxing factor(s) (EDRF) via a cytochrome P450-dependent epoxygenase or non-enzymatic lipid peroxidation pathway----release of EDRF----diffusion of EDRF to the smooth muscle cell; Smooth muscle cell: activation of guanyl cyclase----activation of protein kinase----protein phosphorylation----dephosphorylation of myosin light chain----relaxation. Relationships between endothelium-dependent and endothelium-independent vasorelaxation are indicated. EDRF-candidates include aldehydes and epoxides.
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PMID:Mechanism of endothelium-dependent vasorelaxation. 286 27

The ability of LY83583 to antagonize vascular smooth muscle relaxation elicited by a number of vasodilators was examined in rings of rat aorta. LY83583 (0.3-10 microM) inhibited relaxant responses to acetylcholine, calimycin (A23187), adenosine triphosphate (ATP) and sodium nitroprusside, whereas responses to atriopeptin III an activator of particulate guanylate cyclase, and papaverine were unaffected. For acetylcholine and calimycin the major effect of LY83583 (0.3-10 microM) was to reduce the maximal response without appreciably altering the EC50 values whereas for ATP the EC50 values were markedly increased by low concentrations of LY83583 (0.3-1 microM) with depression of maximal responses occurring at higher concentrations (10 microM) of the antagonist. In contrast LY83583 produced nonparallel rightward shifts of the curve for sodium nitroprusside without altering the maximal response. In addition, LY83583 (10 microM) reduced basal levels of cyclic GMP and prevented acetylcholine and sodium nitroprusside-induced elevations of cyclic GMP, in parallel with reductions in the relaxant responses. In the presence of LY83583 (10 microM) higher concentrations of sodium nitroprusside restored both the relaxant response and the elevation of cyclic GMP. The results of this study show that LY83583 antagonises only those vasodilators which are thought to act via stimulation of soluble guanylate cyclase. The nonsurmountable inhibition of relaxation to acetylcholine, calimycin and ATP probably reflects a limited maximal capacity of the endothelium to release EDRF in response to these agents.
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PMID:Inhibition of vascular smooth muscle relaxation by LY83583. 290 Apr 75

Recent studies on endothelium-dependent vasorelaxation have been briefly reviewed and analyzed. The following processes appear to subserve this mechanism: In the endothelial cell: receptor activation, activation of phospholipases, mobilization of intracellular Ca2+, synthesis and release of 'endothelium-derived relaxing factor(s) (EDRF); In the smooth muscle cell: activation of guanyl cyclase and protein kinase, protein phosphorylation/dephosphorylation, relaxation. Alterations of this mechanism could be involved in certain cardiovascular disorders.
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PMID:Endothelium-derived relaxing factor (EDRF). 300 57

cGMP appears to be the intracellular messenger involved in smooth muscle relaxant effects of three major groups of vasodilators, the ANFs, the nitrovasodilators (such as nitroglycerin, sodium nitroprusside, sodium nitrite, isosorbide dinitrate), and the endothelium-dependent vasodilators (such as ACh, histamine, bradykinin, adenosine triphosphate, A23187). The endothelium-dependent vasodilators apparently act by stimulating the release of EDRF from endothelial cells, which in turn activates soluble guanylate cyclase in vascular smooth muscle cells. Because of similarities between EDRF and the nitrovasodilators, EDRF has been termed the "endogenous nitrovasodilators." Very recent evidence suggests that EDRF may be identical with nitric oxide, the intermediate substance generated by the nitrovasodilators, thus further illustrating the similarities between nitrovasodilator-induced and endothelium-dependent vasodilation. Following the elevation of cGMP levels in smooth muscle, cGMP-kinase becomes activated and phosphorylates cellular protein or proteins involved in the regulation of cytosolic free Ca2+ concentrations. This mechanism vasoconstrictor. In the absence of vasoconstrictors, cGMP, even at basal levels, seems to be important for maintaining cytosolic Ca2+ at low concentrations and for keeping the vascular smooth muscle in a relatively relaxed state. Future experiments will need to clarify further the role of cGMP and cGMP-kinase in physiologic and pathophysiologic regulation of blood vessels. Of prime interest is the identity of functional substrates for cGMP-kinase in vascular smooth muscle.
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PMID:Molecular mechanisms of endothelium-mediated vasodilation. 305 34

Many physiological important substances elicit a relaxing effect on blood vessels which is mediated by (a) substance(s) [EDRF(s)] released from the endothelial cells. EDRF(s) stimulate(s) guanylate cyclase, increasing cGMP at the smooth muscle level, resulting in relaxation. Since this mechanism of action is very similar to that of nitrovasodilator substances, we investigated whether EDRF(s) would act via the "organic nitrate receptor", which is thought to be the common site of action for organic nitrovasodilator substances. The relaxation effect of EDRF-mediated substances (histamine and acetylcholine) was investigated on contracted rat aorta preparations in which the affinity of the organic nitrate receptor was lowered by a treatment with high doses of nitroglycerin. The dose-relaxation curve of nitroglycerin on aorta preparations of pre-treated animals showed a highly significant shift to the right compared to preparations of control rats, proving the nitrate-receptor tolerance. However, when the same preparations were tested for their reactivity to acetylcholine or histamine, no differences could be demonstrated. These results indicate that, although it is known that organic nitrates and EDRF relax vascular smooth muscle cells by stimulating guanylate cyclase, this stimulation is mediated by a different mechanism.
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PMID:Influence of vascular tolerance to nitroglycerin on endothelium-dependent relaxation. 312 95

The aim of this study was to define the roles of extra- and intracellular Ca++ in the release of PGI2 and EDRF from cultured bovine endothelial cells stimulated with receptor-mediated and receptor-independent substances. The receptor-mediated stimulant bradykinin (10 nM) elicited transient releases of PGI2 (assayed with radioimmunoassay of 6-keto PGF1 alpha) and EDRF (assayed by its stimulatory effect on purified soluble guanylate cyclase). Bradykinin also elicited dose-dependent increases in intracellular free calcium [( Cai++], measured with the fluorescent probe indo-1). In the absence of extracellular Ca++ (nominally Ca+(+)-free, EGTA 0.1 mM) or in the presence of the intracellular calcium antagonist TMB-8 (0.1 mM), PGI2 release was significantly attenuated. Bradykinin-induced EDRF release was not significantly affected by TMB-8 but was completely abolished in Ca+(+)-free medium. When endothelial cells were stimulated with thimerosal (an inhibitor of the enzyme acyl-CoA-lysolecithin-acyl-transferase; 5 microM), a long-lasting release of EDRF and PGI2 was induced, associated with only a slight increase in [Cai++]. Removal of extracellular Ca++ had little effect on [Cai++], completely abolished EDRF release, and did not change PGI2 release. It is concluded that there is a close association between PGI2 release and [Cai++] in bradykinin-stimulated endothelial cells. In contrast to PGI2 synthesis, EDRF production is directly dependent on extracellular Ca++ and independent of [Cai++].
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PMID:Release of prostacyclin and EDRF from endothelial cells is differentially controlled by extra- and intracellular calcium. 315 25

Isolated perfused rat kidney was used to examine the possible mechanisms involved in the hypotensive/vasodilator actions of cryptolepine. In kidneys preconstricted by phenylephrine (PE 5-7.5 x 10(-7) M), cryptolepine at bolus doses of 2.5, 5, and 10 micrograms elicited dose-dependent reductions in perfusion pressure by 29.8 +/- 4.1, 43.3 +/- 3.9, and 54.3 +/- 4.9 mm Hg, respectively. In the presence of indomethacin, cryptolepine-induced reduction in perfusion pressure was not significantly changed, suggesting a lack of a cyclooxygenase-mediated component in its renal vasodilator response. Removal of the endothelium with p-bromophenacyl bromide (p-BPB 10 microM) inhibited the vasodilator response to cryptolepine 2.5, 5, and 10 micrograms to 10.2 +/- 1.8, 15.9 +/- 1.5, and 20.2 +/- 2.0 mm Hg, respectively (p < 0.01). The vasodilator response to acetylcholine (ACh 50 ng) was also reduced from a control value of 56.7 +/- 4.5 to 15.3 +/- 1.9 mm Hg (p < 0.01); responses to sodium nitroprusside (SNP 5 micrograms) and isoprenaline (1 microgram) were not affected. In kidneys treated with hydroquinone (10(-5) and 10(-4) M), a specific inhibitor of endothelium-dependent vasodilation, cryptolepine- and ACh-induced vasodilation were inhibited dose dependently (p < 0.01). N omega-nitro-L-arginine (L-NNA 10(-5)-10(-4) M), a specific inhibitor of the synthesis/release of endothelium-derived relaxing factor/nitric oxide (EDRF/NO), attenuated the vasodilator response to cryptolepine and ACh (50 ng) dose dependently. At 10(-4) M L-NNA, cryptolepine-induced vasodilation was reduced to 6.6 +/- 2.2 (2.5 micrograms), 10.9 +/- 2.2 (5 micrograms), and 13.3 +/- 1.4 mm Hg (10 micrograms). L-Arginine (10(-4) and 3 x 10(-4) M) but not D-arginine (10(-4) M) inhibited the effects of L-NNA, with vasodilatory effects of cryptolepine returning to control values, suggesting that the vasodilator material released by cryptolepine is EDRF, possibly NO. Methylene blue (MB 10(-4) M), the inhibitor of soluble guanylate cyclase which inhibited 50 ng ACh and 5 micrograms SNP-induced vasodilation also reduced the vasodilatory responses to cryptolepine to 0.8 +/- 0.8 (2.5 micrograms), 4.2 +/- 4.2 (5 micrograms), and 10.8 +/- 6.2 mm Hg (10 micrograms) suggesting that the effector pathway for cryptolepine-induced vasodilation is soluble guanylate cyclase-linked increase in cyclic GMP of vascular smooth muscle.
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PMID:Role of the endothelium and cyclic GMP in renal vasodilator responses to cryptolepine in rats. 751 10

Endothelium-derived relaxing factor/nitric oxide (EDRF/NO) is produced by the vascular wall and is a key modulator of vascular tone and blood pressure. Since reduced EDRF/NO release from the endothelium is a major key event in the development of atherosclerosis, we investigated the effect of cholesterol on endothelial cell particulate (membrane-bound) NO synthase activity. Low concentrations (up to 0.2 mM) of liposomal cholesterol progressively activated plasma membrane-bound NO synthase. Increasing cholesterol concentration above that which maximally stimulated enzyme activity produced a progressive inhibition with respect to the control value. In time course experiments using endothelial cell plasma membranes enriched with cholesterol, changes in NO production were followed by analogous changes in soluble guanylate cyclase activity (sGC). N-Monomethyl-L-arginine (L-NMMA) (1 mM) inhibited particulate NO synthase activity at all cholesterol concentrations used with subsequent decreases in cGMP production. Egg lecithin liposomes (free of cholesterol) had no effect on NO synthase activity. A three-fold increase in superoxide (O2-) and a 2.5-fold increase in NO formation followed by an eight-fold increase in peroxynitrite (ONOO-) production by cholesterol-treated microsomes isolated from endothelial cells was observed, one which rose further up to eight-fold in the presence of superoxide dismutase (SOD) (10 U/mL). Cholesterol had no effect on Lubrol-PX solubilized membrane-bound NO synthase or on cytosolic (soluble) NO synthase activities of endothelial cells. Cholesterol modulated lipid fluidity of plasma membranes labelled with 1,6-diphenyl-1,3,5-hexatriene (DPH) as indicated by the steady state fluorescence anisotropy [(ro/r)-1]-1. Arrhenius plots of [(ro/r)-1]-1 indicated that the lipid phase separation of the membranes at 26.2 +/- 1.5 degrees was elevated to 34.4 +/- 1.9 degrees in cholesterol-enriched membranes, consistent with a general decrease in membrane fluidity. Cholesterol-enriched plasma membranes treated with egg lecithin liposomes showed a lipid phase separation at 27.5 +/- 1.6 degrees, indicating the reversible effect of cholesterol on membrane lipid fluidity. Arrhenius plots of NO synthase activity exhibited break point at 26.9 +/- 1.8 degrees which rose to 35.6 +/- 2.1 degrees in 0.5 mM cholesterol-treated plasma membranes and decreased to 21.5 +/- 1.4 degrees in plasma membranes treated with 0.2 mM cholesterol. The allosteric properties of plasma membrane-bound NO synthase inhibited by Mn2+ (as reflected by changes in the Hill coefficient) were changed by cholesterol, consistent with modulations of the fluidity of the lipid microenvironment of the enzyme.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Modulation of particulate nitric oxide synthase activity and peroxynitrite synthesis in cholesterol enriched endothelial cell membranes. 754 Mar 91

Recent investigations have suggested that the vascular endothelium is an active participant in the regulation of arterial tone and blood flow. In a state of health, the endothelium contributes to hemodynamic equilibrium; however, it rapidly becomes dysfunctional in hypercholesterolemia and diabetes mellitus or with exposure to the stress of hypertension or long-term smoking. Among the deficits observed during endothelial dysfunction is a reduction in the synthesis and release or an excessive degradation of EDRF. This potent vasorelaxant is derived from the amino acid L-arginine and has been characterized as NO or a closely related substance. EDRF relaxes vascular smooth muscle by activating guanylate cyclase. A deficiency in the activity of EDRF may be the mechanism of diminished coronary vasodilation in patients with ischemic heart disease. Organic nitrates, which are metabolized to NO or S-nitrosothiol at the cellular level, are often used in the management of myocardial ischemia; they also induce vasodilation by activating guanylate cyclase. The similarities between organic nitrates and endogenous EDRF and their interactions are discussed in this review.
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PMID:Endothelium, coronary vasodilation, and organic nitrates. 783 12

Bradykinin (BK), a known vasodilator in vivo, and arginine vasopressin (AVP), a vasoconstrictor in vivo, both stimulate a rise in cytosolic free Ca2+ ([Ca2+]i) in vascular smooth muscle cells (VSMC). The present study was undertaken to investigate this apparent paradox. The following three possibilities were examined, namely, 1) signaling events other than [Ca2+]i are different for BK and AVP; 2) BK, but not AVP, stimulates prostaglandins in VSMC, thus resulting in divergent effects on VSMC tone; and 3) AVP and BK exhibit qualitatively similar effects on VSMC signal transduction but divergent effects on VSMC tone are mediated by endothelial events. The results demonstrated that BK stimulated a rise in inositol trisphosphate (IP3), [Ca2+]i, 45Ca2+ efflux, and Ca2+ influx and a biphasic change in intracellular pH when N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered solution was used. The BK-induced VSMC contraction was also comparable to that observed with AVP. The cyclooxygenase inhibitor, meclofenamate, enhanced the effect of both BK and AVP on VSMC tone, as assessed by shape change, by a comparable degree. BK, but not AVP, stimulated endothelial cells to release a substance that blocked the contractile response of BK and AVP. Methylene blue, a blocker of cytosolic guanylate cyclase and therefore of the production of guanosine 3',5'-cyclic monophosphate (2nd messenger of endothelium-derived relaxing factor, EDRF), and nordihydroguaiaretic acid, an inhibitor of EDRF, both prevented this endothelium-dependent effect of BK. These results therefore indicate that BK is a constrictor of VSMC, an effect that can be overridden by the hormone's endothelial effect to stimulate the release of a vasodilator(s), which is most likely EDRF.
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PMID:Bradykinin: potential for vascular constriction in the presence of endothelial injury. 844 42


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