n-hydroxy-n--(4-butyl-2-methylphenyl)formamidine and Body-Weight

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

1 This study examined the contribution of cytochrome P450 metabolites of arachidonic acid in mediating ischaemia/reperfusion (I/R)-induced cardiac dysfunction in normal and diabetic rats. 2 We first compared the metabolism of arachidonic acid in microsomes prepared from the hearts of control rats and rats treated with streptozotocin (55 mg kg(-1)) to induce diabetes. The production of dihydroxyeicosatrienoic acids and epoxyeicosatrienoic acids (EETs) were similar in microsomes prepared from the hearts of control and diabetic rats, but the production of 20-hydroxyeicosatetraenoic acid (20-HETE) was two-fold higher in diabetic hearts than in control animals. 3 We then compared the change in left ventricular pressure (P(max)), left ventricular end-diastolic pressure, coronary flow and coronary vascular resistance in isolated perfused hearts obtained from control and diabetic animals after 40 min of global ischaemia (I) followed by 30 min of reperfusion (R). The decline in cardiac function was three- to five-fold greater in the hearts obtained from diabetic vs. control animals. 4 Pretreatment of the hearts with N-hydroxy-N'-(4-butyl-2-methyl-phenyl)-formamidine (HET0016, 1 microm), a selective inhibitor of the synthesis of 20-HETE, for 30 min before I/R resulted in significant improvement in the recovery of cardiac function in the hearts obtained from diabetic but not in control rats. Perfusion with an inhibitor of soluble epoxide hydrolase, 1-cyclohexyl-3-dodecyl urea (CDU), before I/R improved the recovery of cardiac function in hearts obtained from both control and diabetic animals. Perfusion with both HET0016 and CDU resulted in significantly better recovery of cardiac function of diabetic hearts following I/R than that seen using either drug alone. Pretreatment of the hearts with glibenclamide (1 microm), an inhibitor of ATP-sensitive potassium channels, attenuated the cardioprotective effects of both CDU and HET0016. 5 This is the first study to suggest that acute blockade of the formation of 20-HETE and/or reduced inactivation of EETs could be an important strategy to reduce cardiac dysfunction following I/R events in diabetes.

Topics: 8,11,14-Eicosatrienoic Acid; Amidines; Animals; Arachidonic Acid; Blood Glucose; Body Weight; Coronary Circulation; Cytochrome P-450 Enzyme System; Diabetes Mellitus, Experimental; Enzyme Inhibitors; Epoxide Hydrolases; Glyburide; Heart; Hydroxyeicosatetraenoic Acids; Male; Microsomes; Myocardium; Rats; Rats, Wistar; Reperfusion Injury; Urea; Vascular Resistance; Ventricular Dysfunction, Left

20-hydroxyeicosatetraenoic acid (20-HETE) is a potent constrictor in small arteries and also has natriuretic properties. Urinary 20-HETE excretion is increased in adrenocorticotrophic hormone (ACTH)-induced hypertensive rats. In the present study, we investigated the effect of a specific enzyme inhibitor of 20-HETE production, N-hydroxy-N'-(4-butyl-2-methylphenyl) formamidine (HET0016), on glucocorticoid-induced hypertension in rats, a sodium-independent model.. Male Sprague-Dawley rats were treated with physiological saline (0.9% NaCl), ACTH (0.2 mg/kg per day) or dexamethasone (0.03 mg/rat per day) subcutaneously for 13 days. HET0016 (10 mg/kg per day) or its vehicle (10% lecithin in physiological saline) was coadministered (intraperitoneally) a day before (prevention study) or at day 8 of treatment (reversal studies). Systolic blood pressure was measured by the tail-cuff method.. Relative to physiological saline, systolic blood pressure was increased by ACTH (P < 0.001) and dexamethasone (P < 0.01). HET0016 reversed ACTH-induced (P < 0.01) but not dexamethasone-induced hypertension. HET0016 also prevented the development of hypertension induced by ACTH (P < 0.01). ACTH, but not dexamethasone, increased renal microsome 20-HETE formation and plasma F2-isoprostane concentrations. HET0016 inhibited renal 20-HETE formation but had no effect on plasma F2-isoprostane concentrations or renal cytochrome P450 4A1 expression.. Inhibition of 20-HETE production by HET0016 prevents and reverses ACTH-induced but not dexamethasone-induced hypertension. These results suggest that 20-HETE may play a role in the genesis of ACTH-induced hypertension but not in dexamethasone-induced hypertension.

Topics: Adrenocorticotropic Hormone; Amidines; Animals; Body Weight; Dexamethasone; F2-Isoprostanes; Hydroxyeicosatetraenoic Acids; Hypertension; Kidney; Male; Organ Size; Rats; Rats, Sprague-Dawley; Reactive Nitrogen Species; Systole