endothelin-1 and 1-aminobenzotriazole

1 This study examined the role of 20-hydroxyeicosatetraenoic (20-HETE) in altering vascular function in streptozotocin (STZ)-induced diabetic rats. 2 The expression of CYP4A protein and the formation of 20-HETE were elevated in the kidney, but not in the renal or mesenteric vasculature, of diabetic animals. The vasoconstrictor responses to norepinephrine (NE), endothelin-1 (ET-1), and angiotensin II (Ang II) were significantly enhanced in the isolated perfused mesenteric vascular bed and renal artery segments of diabetic rats. Chronic treatment of the diabetic rats with 1-aminobenzotriazole (ABT, 50 mg kg(-1) alt(-1) diem) or N-hydroxy-N'-(4-butyl-2-methylphenyl) formamidine (HET0016, 2.5 mg kg(-1) day(-1)) attenuated the responses to these vasoconstrictors in both vascular beds. 3 The synthesis of 20-HETE in renal microsomes was reduced by >80% confirming that the doses of ABT and HET0016 were sufficient to achieve system blockade. Addition of HET0016 (1 microM) in vitro also normalized the enhanced vascular responsiveness of renal and mesenteric vessels obtained from diabetic animals to NE and inhibited the formation of 20-HETE by >90% while having no effect on the formation of epoxides. Vasodilator responses to carbachol and histamine were reduced in the mesenteric vasculature, but not in renal arteries, of diabetic rats. Treatment of the diabetic animals with HET0016 improved vasodilator responses in both vascular beds. Vascular sensitivity to exogenous 20-HETE was elevated in the mesenteric bed of diabetic animals compared to controls. 4 These results suggest that 20-HETE contributes to the elevation in vascular reactivity in diabetic animals. This effect is not due to increased vascular expression of CYP4A but may be related to either enhanced agonist-induced release of substrate (arachidonic acid) by the CaMKII/Ras-GTPase system and/or elevated vascular responsiveness to 20-HETE by the CaMKII/Ras-GTPase system and/or elevated vascular responsiveness to 20-HETE.

Topics: Amidines; Angiotensin II; Animals; Blood Glucose; Body Weight; Carbachol; Cytochrome P-450 CYP4A; Diabetes Mellitus, Experimental; Endothelin-1; Enzyme Inhibitors; Histamine; Hydroxyeicosatetraenoic Acids; Kidney; Male; Mesenteric Arteries; Microsomes; Nitroprusside; Norepinephrine; Perfusion; Rats; Rats, Wistar; Renal Artery; Triazoles; Vasoconstriction; Vasodilation

The present study evaluated the contribution of 20-hydroxyeicosatetraenoic acid (20-HETE) and its interaction with nitric oxide (NO) in cyclosporin A-induced nephrotoxicity and hypertension.. The treatment of rats with cyclosporin A (25 mg/kg) for 7 days increased the renal microsomal conversion of arachidonic acid (AA) to 20-HETE (93 +/- 6%, P < 0.05), increased systolic blood pressure (SBP), reduced the urinary excretion of nitrite (53 +/- 8%, P < 0.05), induced renal damage as indicated by a marked increase in protein excretion (163 +/- 14%, P < 0.05), increased renal vasoconstrictor responses to AA (82 +/- 5%, P < 0.05) but not endothelin-1 or phenylephrine, and decreased vasodilator responses to bradykinin (42 +/- 10%, P < 0.05) and sodium nitroprusside (SNP; 56 +/- 13%, P < 0.05) in the renal preglomerular vessel treated with indomethacin and NO synthase inhibitor. The pretreatment of rats with HET0016 (10 mg/kg) or 1-aminobenzotriazole (50 mg/kg), inhibitors of cytochrome P450 (CYP450) activity, attenuated or prevented cyclosporin A-induced increases in 20-HETE production, SBP, and protein excretion, as did L-arginine (4 g/l), a substrate for NO synthase. L-Arginine but not HET0016 or 1-aminobenzotriazole blunted the cyclosporin A-induced decrease in nitrite excretion. Similarly, L-arginine blunted the enhanced vasoconstriction by AA as did HET0016 or 1-aminobenzotriazole. However, cyclosporin A-blunted dilator responses to bradykinin and SNP were not affected by L-arginine, HET0016, or 1-aminobenzotriazole.. These data suggest that cyclosporin A-induced nephrotoxicity can be accounted for by reduced NO production and a consequent increase in 20-HETE. The cyclosporin A-induced nephrotoxicity is thus an ideal model for evaluating NO/CYP450 interactions.

Topics: Amidines; Animals; Arginine; Blood Pressure; Bradykinin; Cyclosporine; Cytochrome P-450 Enzyme System; Endothelin-1; Hydroxyeicosatetraenoic Acids; Kidney; Male; Microsomes; Nitric Oxide; Nitroprusside; Phenylephrine; Rats; Rats, Sprague-Dawley; Triazoles