Formation of monohydroxyeicosatetraenoic acids from arachidonic acid by cultured rabbit aortic smooth muscle cells

1 We have examined the effects of inhibition of nitric oxide synthase, cyclo-oxygenase and lipoxygenase on the responses of renal arcuate arteries of Wistar rats, with and without endothelium, to noradrenaline, potassium chloride, endothelin-l, acetylcholine and sodium nitroprusside. 2 Noradrenaline, potassium chloride and endothelin-1 caused concentration-dependent contraction of the vessels. Indomethacin (14 fLM) attenuated the contractile response to noradrenaline and to potassium chloride. The inhibitory effect of indomethacin persisted following endothelial removal. 3 Acetylcholine produced concentration-dependent relaxation of the vessels which was potentiated by indomethacin (14 gM). 4 NG-nitro-L-arginine methyl ester (L-NAME, 100 gM) did not affect the contractile response to either noradrenaline or potassium chloride but abolished relaxation to acetylcholine. In addition, L-NAME abolished the affects of indomethacin on acetylcholine-induced relaxation and noradrenaline-and potassium chloride-induced contraction. 5 BWC755C attenuated noradrenaline and potassium chloride-induced contraction. This effect persisted in the presence of indomethacin. 6 In vessels pretreated with CHAPS, BW755C inhibited both noradrenaline and potassium chlorideinduced contraction. In these vessels BW755C had no additional inhibitory effect to indomethacin on noradrenaline-and potassium-induced contraction.7 Inhibition of nitric oxide synthase with L-NAME (1001iM) attenuated the effect of BW755C on noradrenaline-and potassium-induced contraction. 8 BW755C alone did not affect endothelium-dependent relaxation as assessed by the response to acetylcholine. However, in the presence of indomethacin, BW755C inhibited acetylcholine-induced relaxation. 9 BW755C did not affect endothelium-independent relaxation as assessed by the response to sodium nitroprusside in vessels with or without endothelium. 10 These data support the existence of two vasoconstrictor products of arachidonic acid released during contraction of renal arcuate arteries with noradrenaline and potassium chloride. A cyclooxygenase product which appears to be endothelium-independent and the other an endotheliumdependent lipoxygenase product.

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Relative roles of nitric oxide and cyclo‐oxygenase and lipoxygenase products of arachidonic acid in the contractile responses of rat renal arcuate arteries

Richards

Michael

et al. 1994

“…Lipoxygenase activity (5-, 12-, 15-) has been demonstrated LIPOXYGENASE, CYCLO-OXYGENASE AND MESENTERIC ARTERIES 361 within the endothelium and vascular smooth muscle from a variety of vascular beds in all species studied (Larrue et al, 1983;Farber et al, 1985;Revtyak et al, 1988;Shannon et al, 1991). The main vasoactive products of the 5-lipoxygenase enzyme are leukotriene C4 and leukotriene D4.…”

Section: Introductionmentioning

confidence: 99%

“…12-HETE, a product of the 12-lipoxygenase pathway, is a directly acting vasoconstrictor , and contributes to the effector mechanisms of angiotensin II-induced vasoconstriction and modulates the intracellular calcium response to arginine vasopressin, angiotensin II and endothelin (Saito et al, 1992). 15-HETE is the major lipoxygenase product of cultured endothelial cells (Larrue et al, 1983) and of the atherosclerotic vessel wall (Henriksson et al, 1985). It is also a directly acting vasoconstrictor in a number of vascular beds of the dog and under certain circumstances may act as an endothelium-independent vasodilator (Van Diest et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Interdependence of contractile responses of rat small mesenteric arteries on nitric oxide and cyclo‐oxygenase and lipoxygenase products of arachidonic acid

Johns

Michael

et al. 1994

1 We have examined the effects of nitric oxide inhibition, indomethacin and the dual lipoxygenase/ cyclo-oxygenase inhibitor, 3-amino-l-[m-(trifluoromethyl)-phenyl]-2-pyrazoline (BW755C), on the responses of small mesenteric arteries of Wistar rats, with and without endothelium, to noradrenaline, potassium chloride, endothelin-1, acetylcholine and sodium nitroprusside. 2 Noradrenaline, potassium chloride and endothelin-l caused concentration-dependent contraction of small mesenteric arteries. Indomethacin (14 iM) attenuated the contractile response to both noradrenaline and potassium chloride. The inhibitory action of indomethacin persisted in vessels treated with CHAPS. 3 Acetylcholine produced concentration-dependent relaxation in these vessels. Indomethacin (14JM) had no significant effect on the acetylcholine concentration-response relationship. 4 NG-nitro-L-arginine methyl ester (L-NAME, 100 LM) potentiated the contractile response to both noradrenaline and potassium chloride and inhibited acetylcholine-induced relaxation. Indomethacin attenuated the effects of L-NAME. 5 BW755C inhibited the contractile response to noradrenaline and potassium chloride but not to endothelin-1. The inhibitory effects of BW755C persisted in the presence of indomethacin and in vessels treated with CHAPS. 6 BW755C enhanced endothelium-dependent relaxation, as assessed by the response to acetylcholine. In the presence of indomethacin, BW755C produced a shift to the right of the concentration-response curve to acetylcholine. 7 Inhibition of nitric oxide synthase with L-NAME, reversed the inhibitory effect of BW755C on noradrenaline-and potassium-induced contraction. L-NAME and BW755C in combination resulted in a shift to the right of the concentration-response curve to acetylcholine. 8 Sodium nitroprusside produced concentration-dependent relaxation of the vessels. Endothelium removal reduced the maximum relaxation to nitroprusside. BW755C did not alter the response to sodium nitroprusside in vessels with or without endothelium. 9 These data support the existence of two vasoconstrictor products of arachidonic acid released during contraction of small mesenteric arteries with noradrenaline and potassium chloride: a cyclo-oxygenase product and a lipoxygenase product both of which appear to be largely endothelium-independent.

“…Alternative pathways for arachidonic acid metabolism have been described in vascular tissue. Lipoxygenases and cytochrome P450 epoxygenase metabolize arachidonic acid to various biologically active hydroperoxy-, hydroxy-, dihydroxyeicosatetraenoic acids and leukotrienes (Juchau et al, 1976;Greenwald et al, 1979;Larrue et al, 1983). More recently we have described the release of hydroxy epoxide metabolites of arachidonic acid named hepoxilins by vascular tissue (Laneuville et al, 1991a).…”

Section: Introductionmentioning

confidence: 99%

Hepoxilins sensitize blood vessels to noradrenaline—stereospecificity of action

Laneuville

Couture

Pace-Asciak

1992

1 The vascular activity of two stereoisomers of hepoxilin A3 (HxA3) (8R and 8S) and of its glutathione conjugate, hepoxilin A3-C (HxA3-C) (8R and 8S), was investigated on rat helicoidal strips of thoracic aorta and longitudinal strips of portal vein.2 Neither of the hepoxilins tested had a direct effect on the tone of the aortic strip or on the spontaneous contractions of the portal vein. However, the noradrenaline (NA)-induced response of these vessels, as expressed by the dose required for half maximal contraction, (EC50) was greater in HxA3 (8S)-and HxA3-C (8R)-treated aorta. Increased frequency and strength of spontaneous contractions of the portal vein were detected at lower concentrations of NA in the presence of hepoxilins. 3 The threshold dose for both hepoxilins was 10-8M and their effect was not dose-related beyond 10-8m. The effect of hepoxilin appeared after a 45min incubation period and could be observed even if the compounds were washed out after 15 min. 4 Stereochemical specificity was observed. The 8S isomer of HxA3 was active in potentiating the NAinduced contraction of these vessels while the 8R isomer was inactive. In contrast, the 8R isomer of HxA3-C was active while the 8S isomer was inactive. In both tissues, HxA3 (8S) was more potent than its glutathione conjugate, HxA3-C (8R).5 In calcium-free buffer or in the presence of a calcium channel blocker (nifedipine 1 pM), no potentiation of NA-induced contraction by hepoxilins could be observed, suggesting the involvement of extracellular calcium in the actions of hepoxilins. 6 These experiments suggest that hepoxilins may be involved in the modulation of vascular tone and contractility.