Cytochrome P-450-derived eicosanoids participate in the renal functional effects of ET-1 in the anesthetized rat

We evaluated the contribution of cytochrome P-450 (CYP450)-dependent arachidonic acid (AA) metabolites and prostanoids to the renal hemodynamic and tubular effects of endothelin-1 (ET-1) in anesthetized rats. Either ET-1 (0.3, 1.0, and 3 pmol.kg(-1).min(-1)) or vehicle was infused intravenously during two to three 30-min clearance experimental periods. Only high-dose ET-1 increased mean arterial pressure: control, 75 +/- 3 mmHg vs. experimental, 84 +/- 4 mmHg. A dose-dependent diuretic-natriuretic response to ET-1 occurred despite progressive declines in glomerular filtration rate (GFR) and renal blood flow. In the face of a 36% reduction in GFR in response to the highest dose of ET-1, urinary sodium excretion (UNaV) increased threefold from 0.57 +/- 0.11 to 1.6 +/- 0.10 mu mol.100 g(-1).min(-1). Indomethacin (5 mg/kg) decreased basal GFR from 1.2 +/- 0.3 ml.100 g(-1).min(-1) to 0.8 +/- 0.1 ml.100 g(-1).min(-1) and potentiated the GFR lowering action of ET-1 associated with reductions in UNaV and urine volume. Cobalt chloride (CoCl2) and dibromododec-11-enoic acid (DBDD), which diminish CYP450-dependent AA metabolism through different mechanisms, were used to identify CYP450 products mediating the renal functional actions of ET-1. DBDD (12.5 mu g/min) reduced urinary excretion of 20-hydroxyeicosatetraenoic acid from 3.4 +/- 0.9 (control) to 1.1 +/- 0.6 ng/h and abolished the negative effects of ET-1 on GFR while decreasing the diuretic-natriuretic action of ET-1. Similar effects were produced by CoCl2. Clotrimazole, an inhibitor of epoxygenase activity, was without effect on ET-1-induced renal functional changes. Thus the capacity of ET-1 to enhance prostaglandin production was primarily expressed in terms of positive effects on renal hemodynamics. In contrast, CYP450 products promoted sodium excretion despite negative effects on renal hemodynamics.