Oxygen free radical-induced injury in isolated rat hearts: effects of ibuprofen and BW 755c

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

1. We have examined the effects of nitric oxide inhibition, indomethacin and the dual lipoxygenase/cyclo-oxygenase inhibitor, 3-amino-1-[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-1 caused concentration-dependent contraction of small mesenteric arteries. Indomethacin (14 microM) 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 (14 microM) had no significant effect on the acetylcholine concentration-response relationship. 4. NG-nitro-L-arginine methyl ester (L-NAME, 100 microM) 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.

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

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-1, acetylcholine and sodium nitroprusside. 2. Noradrenaline, potassium chloride and endothelin-1 caused concentration-dependent contraction of the vessels. Indomethacin (14 microM) 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 microM). 4. NG-nitro-L-arginine methyl ester (L-NAME, 100 microM) 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 chloride-induced 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 (100 microM) 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 endothelium dependent lipoxygenase product.

Mediatory role of copper in reactive oxygen intermediate-induced cardiac injury

In this report the mediatory role of copper in cardiac injury produced by reactive oxygen intermediates was examined. Isolated rat hearts were perfused with Krebs-Henseleit buffer containing 0.25 mM ascorbate plus varying concentrations of copper-bis-histidial for up to 60 min. Using salicylate as a probe, OH generation by this system was demonstrated. Copper or ascorbate alone had minimal effect on cardiac function as determined by heart rate, coronary flow, left ventricular systolic pressure development, end diastolic pressure and +/- dP/dtmax. Copper, from 0.5 microM to 20 microM, and ascorbate, 0.25 mM, resulted in concentration-dependent decreases in all of the experimental variables. Treatment with 5 or 20 microM copper resulted in complete loss of cardiac function within 40 and 30 min, respectively. By 30 min, 5 microM copper had resulted in increased end diastolic pressure to greater than 40 mmHg. By 60 min, perfusion with 1 microM copper resulted in almost 100% loss of function and end diastolic pressure greater than 25 mmHg. Copper, 0.5 microM, also decreased cardiac function, but to a lesser degree. Catalase, 100 units/ml, was effective in preventing the copper-ascorbate induced cardiac damage while superoxide dismutase, 25 units/ml, was ineffective. Observations by light and electron microscopy demonstrated patchy regions with vacuolization corresponding to swollen mitochondria. These results clearly demonstrate that copper-catalyzed redox reactions can induce cardiac injury via a mechanism which appears to be related to the production of OH.