Blackwell Publishing Journal Backfiles 1879-2005
1. A significant renal vasodilation was observed previously after an acute cyclo-oxygenase (COX) inhibition induced with indomethacin. Because this effect could be due to COX-dependent intrarenal metabolization of arachidonic acid through cytochrome P450 (CYP450) pathways, the aim of the present study was to investigate, in vivo, possible interactions between COX and CYP450 mono-oxygenases.2. Mean arterial pressure (MAP) and renal blood flow (RBF), using an electromagnetic flow transducer for RBF evaluation, were measured continuously in 71 anaesthetized euvolaemic rats. Appropriate solvents (vehicle), 3 mg/kg indomethacin, 17-octadecynoic acid (17-ODYA; 2 mmol/L), either miconazole (MI; 1.5 mmol/L) or N-methylsulphonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH; 5 mg/kg) and N′-hydroxyphenylformamidine (HET0016; 5 or 10 mg/kg) were administered to inhibit either COX, CYP450 mono-oxygenases, epoxygenases or hydroxylase, respectively. The CYP450 and COX inhibitors were also combined as follows: 17-ODYA/indomethacin, MI (or MS-PPOH)/indomethacin, HET0016/indomethacin and indomethacin/HET0016.3. Mean arterial pressure and RBF were not modified by vehicle, 17-ODYA or MI (or MS-PPOH). However, MAP decreased slightly (P 〈 0.05; paired t-test, 5 d.f.) and RBF increased transiently (P 〈 0.05; anova, 5 d.f.) after HET0016. In contrast, MAP decreased by 10 mmHg (P 〈 0.05) and RBF increased by 10% (P 〈 0.05) after indomethacin. This enhancement was prevented by 17-ODYA or MI (or MS-PPOH), but not by HET0016. Moreover, RBF increased step-wise to 21% in the indomethacin/HET0016 experiment (P 〈 0.05). Consequently, changes from baseline in renal vascular resistance differed among treatments, averaging −2 ± 3 (vehicle), −13 ± 3 (indomethacin; P 〈 0.05 vs vehicle), −4 ± 3 (17-ODYA/indomethacin), −3 ± 4 (MI or MS-PPOH/indomethacin), −15 ± 3 (HET0016/indomethacin; P 〈 0.05) and −22 ± 4% (indomethacin/HET0016; P 〈 0.05).4. In conclusion, these results demonstrate that the renal vasodilation induced by indomethacin can be prevented by prior inhibition of CYP450 mono-oxygenases and further suggest that the CYP450 epoxygenases pathway may prevail.
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