15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and 2-2--(hydroxynitrosohydrazono)bis-ethanamine

The activity of NADPH oxidase (NOX) is blocked by nitric oxide (NO). Hydrogen sulfide (H(2)S) is also produced by blood vessels. It is reasonable to suggest that H(2)S may have similar actions to NO on NOX. In order to test this hypothesis, the effect of sodium hydrosulfide (NaHS) on O(2)(-) formation, the expression of NOX-1 (a catalytic subunit of NOX) and Rac(1) activity (essential for full NOX activity) in isolated vascular smooth muscle cells (hVSMCs) was investigated. hVSMCs were incubated with the thromboxane A(2) analogue U46619 +/- NaHS for 1 or 16 h, and O(2)(-) formation, NOX-1 expression and Rac(1) activity were assessed. The possible interaction between H(2)S and NO was also studied by using an NO synthase inhibitor, L-NAME, and an NO donor, DETA-NONOate. The role of K(ATP) channels was studied by using glibenclamide. NaHS inhibited O(2)(-) formation following incubation of 1 h (IC(50), 30 nM) and 16 h (IC(50), 20 nM), blocked NOX-1 expression and inhibited Rac(1) activity. These inhibitory effects of NaHS were mediated by the cAMP-protein-kinase-A axis. Exogenous H(2)S prevents NOX-driven intravascular oxidative stress through an a priori inhibition of Rac(1) and downregulation of NOX-1 protein expression, an effect mediated by activation of the adenylylcyclase-cAMP-protein-kinase-G system by H(2)S.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenylyl Cyclases; Cells, Cultured; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cyclic GMP-Dependent Protein Kinases; Dose-Response Relationship, Drug; Enzyme Inhibitors; Glyburide; Humans; Hydrogen Sulfide; KATP Channels; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; NADPH Oxidase 1; NADPH Oxidases; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroso Compounds; Potassium Channel Blockers; rac1 GTP-Binding Protein; Signal Transduction; Sulfides; Superoxides; Time Factors

Adrenal steroidogenesis is modulated by humoral and neuronal factors and blood flow. Angiotensin II (AII) stimulates adrenal cortical aldosterone and cortisol production and medullary catecholamine release. However, AII regulation of adrenal vascular tone has not been characterized. We examined the effect of AII on diameters of cannulated bovine adrenal cortical arteries. Cortical arteries (average internal diameter = 230 microm) were constricted with U46619 and concentration-diameter responses to AII (10(-13) to 10(-8) mol/liter) were measured. In endothelium-intact arteries, AII induced dilations at low concentrations (maximum dilation = 25 +/- 6% at 10(-10) mol/liter) and constrictions at high concentrations (maximum constriction = 25 +/- 18% at 10(-8) mol/liter). AII constrictions were blocked by the angiotensin type 1 (AT1) receptor antagonist, losartan (10(-6) mol/liter). AII dilations were enhanced by losartan (maximal dilation = 48 +/- 8%), abolished by endothelial cell removal or N-nitro-L-arginine (L-NA, 3 x 10(-5) mol/liter) and inhibited by the angiotensin type 2 (AT2) receptor antagonist, PD123319 (10(-6) mol/liter, maximal dilation = 18 +/- 4%). In a 4,5-diaminofluorescein diacetate nitric oxide (NO) assay of isolated cortical arteries, AII stimulated NO production, which was abolished by PD123319, L-NA, or endothelial cell removal. Western immunoblot of arterial homogenates and endothelial and zona glomerulosa cell lysates revealed 48-kD and 50-kD bands corresponding to AT1 and AT2 receptors, respectively, in all three and a 140-kD band corresponding to endothelial NO synthase in endothelial cells and arteries. Our results demonstrate that AII stimulates adrenal cortical arterial dilation through endothelial cell AT2 receptor activation and NO release and AT1 receptor-dependent constriction.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adrenal Cortex; Angiotensin II; Animals; Arterioles; Cattle; Endothelium, Vascular; Losartan; Nitric Oxide; Nitric Oxide Donors; Nitroso Compounds; Vasoconstriction; Vasoconstrictor Agents; Vasodilator Agents

Activation of a soluble guanylyl cyclase plays an important role in nitric oxide (NO)-induced vasodilation. Recently, we have reported that NO increases the calcium-activated potassium (K(Ca)) channel activity in vascular smooth muscle cells from coronary arteries. The present study examined the role of the soluble guanylyl cyclase in the control of basal activity of the K(Ca) channels and in mediating NO-induced activation of the K(Ca) channels in vascular smooth muscle cells, using a selective inhibitor of this enzyme, 1H-[1,2,4]oxadiazolo[4,2-alpha]quinoxalin-1-one (ODQ). In the cell-attached patch-clamp mode, addition of ODQ into the bath solution (10 micromol/L) decreased the K(Ca) channel activity by 59% and attenuated activation of the channels induced by the NO donor, deta nonoate, by 70%. ODQ had no effect on 8-bromo-cGMP-induced activation of the K(Ca) channels. Deta nonoate produced a concentration-dependent relaxation of precontracted coronary arteries. When ODQ was added to the bath, the deta nonoate-induced relaxations were inhibited. The IC50 for deta nonoate was decreased by about 25-fold and the maximal effect of deta nonoate was reduced by about 60%. A specific K(Ca) channel inhibitor, iberiotoxin, decreased deta nonoate-induced vasodilation but to a lesser extent than ODQ. However, ODQ was without effect on the vasodilation induced by a prostacyclin analog, iloprost, and by adenosine. These results indicate that a soluble guanylyl cyclase and cGMP play an important role in the control of the K(Ca) channel activity in coronary arterial smooth muscle cells. K(Ca) channel activation participates in the NO-induced vasodilation in coronary circulation.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenosine; Animals; Cattle; Coronary Vessels; Cyclic GMP; Enzyme Inhibitors; Guanylate Cyclase; Iloprost; In Vitro Techniques; Kinetics; Membrane Potentials; Muscle Contraction; Muscle, Smooth, Vascular; Nitroso Compounds; Oxadiazoles; Patch-Clamp Techniques; Peptides; Potassium Channels; Quinoxalines; Scorpion Venoms; Vasodilation