No abstract

In the rat isolated perfused kidney, 5,8,11,14-eicosatetraynoic acid, an inhibitor of all pathways of arachidonic acid (AA) metabolism, diminished endothelin-1 (ET-1)- and angiotensin II (ANG II)-induced renal vasoconstriction by approximately 60-70%. We then examined the individual contribution of each oxygenase, cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P-450 (CYP) to the vasoconstrictor effects of ET-1 and ANG II. Inhibition of COX with indomethacin reduced by 30-40% the vasoconstrictor responses to ET-1 and ANG II. Inhibition of 12-LOX with baicalein and 5- and 12-LOX with 5,8,11-eicosatriynoic acid attenuated ANG II-induced renal vasoconstriction by approximately 40-60% but did not affect responses to ET-1. In contrast, 12,12-dibromododec-11-enoic acid (DBDD), an inhibitor of the CYP omega/omega 1-hydroxylase pathway, diminished ET-1-induced renal vasoconstriction by 30-40%, an effect reproduced by depletion of CYP enzymes with CoCl2. Neither DBDD nor CoCl2 affected renal vasoconstriction elicited by ANG II. ET-1 increased efflux of 19- and 20-hydroxyeicosatetraenoic acid, an effect reduced by DBDD. Thus products of the COX and CYP pathways contribute to the renal vasoconstrictor response to ET-1, whereas COX- and LOX-derived eicosanoids contribute to the response to ANG II, accounting for > or = 80% of the vasoactivity of the peptides.

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 μmol ⋅ 100 g−1 ⋅ min−1. Indomethacin (5 mg/kg) decreased basal GFR from 1.2 ± 0.3 ml ⋅ 100 g−1 ⋅ min−1to 0.8 ± 0.1 ml ⋅ 100 g−1 ⋅ min−1and 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 μg/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.

1 We tested the hypothesis that nitric oxide (NO) exerts a tonic inhibitory in¯uence on cytochrome P450 (CYP450)-dependent metabolism of arachidonic acid (AA). 2 N o -nitro-L-Arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), increased mean blood pressure (MBP), from 91+6 to 137+5 mmHg, renal vascular resistance (RVR), from 9.9+0.6 to 27.4+2.5 mmHg ml 71 min 71 , and reduced renal blood¯ow (RBF), from 9.8+0.7 to 6.5+0.6 ml min 71 ) and GFR from 1.2+0.2 to 0.6+0.2 ml 100 g 71 min 71 ) accompanied by diuresis (UV, 1.7+0.3 to 4.3+0.8 ml 100 g 71 min 71 ), and natriuresis (U Na V, 0.36+0.04 to 1.25+0.032 mmol 100 g 71 min 71 ). 3 12, 12 dibromododec-enoic acid (DBDD), an inhibitor of o hydroxylase, blunted L-NAME-induced changes in MBP, RVR, UV and U Na V by 63+8, 70+5, 45+8 and 42+9%, respectively, and fully reversed the reduction in GFR by L-NAME. Clotrimazole, an inhibitor of the epoxygenase pathway of CYP450-dependent AA metabolism, was without e ect. 4 BMS182874 (5-dimethylamino)-N-(3,4-dimethyl-5-isoxazolyl)-1-naphthalenesulfonamide), an endothelin (ET) A receptor antagonist, also blunted the increases in MBP and RVR and the diuresis/ natriuresis elicited by L-NAME without a ecting GFR. 5 Indomethacin blunted L-NAME-induced increases in RVR, UV and U Na V., an endoperoxide receptor antagonist, attenuated the pressor and renal haemodynamic but not the renal tubular e ects of L-NAME. 6 In conclusion, the renal functional e ects of the CYP450-derived mediator(s) expressed after inhibition of NOS with L-NAME were prevented by inhibiting either CYP450 o hydroxylase or cyclooxygenase or by antagonizing either ET A or endoperoxide receptors. 20-hydroxyeicosatetraenoic acid (20-HETE) ful®ls the salient properties of this mediator.

Inhibition of cytochrome P-450 (CYP450) enzymes with cobalt chloride (CoCl2) prevented hypertension, organ hypertrophy, and renal injury induced by DOCA and salt (1% NaCl) in uninephrectomized (UNx) rats. Systolic blood pressure (SBP) rose to 193 ± 6 mmHg by day 21 from control levels of 150 ± 7 mmHg in response to DOCA-salt treatment, a rise that was prevented by CoCl2 (24 mg ⋅ kg−1 ⋅ 24 h−1). The effects of DOCA-salt treatment, which increased protein excretion to 88.3 ± 6.9 mg/24 h on day 21 from 9.0 ± 1.1 mg/24 h on day 3, were prevented by CoCl2. CoCl2 also attenuated the renal and left ventricular hypertrophy and the increase in media-to-lumen ratio in hypertensive rats. DOCA-salt treatment increased excretion of endothelin (ET)-1 from 81 ± 17 to 277 ± 104 pg ⋅ 100 g body wt−1 ⋅ 24 h−1 associated with a fourfold increase in 20-hydroxyeicosatetraenoic acid (20-HETE) excretion from 3.0 ± 1.1 to 12.2 ± 1.9 ng ⋅ 100 g body wt−1 ⋅ 24 h−1( days 3 vs. 21). CoCl2 blunted these increases by 58 and 72%, respectively. In aortic rings pulsed with [3H]thymidine, ET-1 increased its incorporation. Dibromododec-11-enoic acid, an inhibitor of 20-HETE synthesis, attenuated ET-1-induced increases in [3H]thymidine incorporation. We distinguished effects of CoCl2 acting via CO generation vs. suppression of CYP450-arachidonic acid metabolism by treating UNx-salt-DOCA rats with 1-aminobenzotriazole (ABT), which suppresses CYP450 enzyme activity, and compared these results to those produced by CoCl2. ABT reduced hypertension, as did CoCl2. Unlike CoCl2, ABT did not prevent organ hypertrophy and proteinuria, suggesting that these effects were partially related to CO formation. Blockade of the ETA receptor with BMS-182874 reduced SBP, organ hypertrophy, and proteinuria, indicating the importance of ET-initiated abnormalities to the progression of lesions in UNx-salt-DOCA.

No abstract

Endothelin-1 (ET-1) produces potent renal effects that we have previously shown to be dependent on cytochrome P-450 (CYP450) metabolites of aracidonic acid (24) This study evaluated the role of these metabolites in the effects produced by ET-1 on renal blood flow (RBF), cortical blood flow (CBF), medullary blood flow (MBF), and mean arterial blood pressure (MBP). ET-1 (20-200 pmol/kg) increased MBP, renal vascular resistance (RVR), and MBF but reduced CBF and RBF in a dose-dependent manner. The decreases in CBF and RBF, and increases in MBP and RVR were blunted by BMS-182874, an ET(A) receptor antagonist or BQ-788, an ET(B) receptor antagonist. Similarly, indomethacin, an inhibitor of cyclooxygenase activity, or 12,12-dibromododecenoic acid (DBDD), a CYP450-dependent inhibitor of production of 20-hydroxyeicosatetraenoic acid (20-HETE), blunted these effects. ET-3 elicited dose-related reduction in CBF and increase in MBF. Indomethacin accentuated the reduction in CBF and attenuated the increase in MBF, as did DBDD. ET-1-induced increase in MBF was attenuated by BQ-788, N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis, indomethacin, or DBDD. DBDD inhibited the hemodynamic effects of L-NAME. Miconazole, the inhibitor of CYP450-dependent epoxygenase activity, was without effect. These results indicate that hemodynamic changes produced by ET-1 are mediated by vasoconstrictor prostanoids and/or prostanoid-like substances, possibly, 20-HETE via activation of ET(A) and ET(B) receptors. However, the increase in MBF is mediated by vasodilator prostanoids or by NO via ET(B) receptor activation.

The Research Centers in Minority Institu­tions (RCMI) program was established by the US Congress to support the develop­ment of biomedical research infrastructure at minority-serving institutions granting doctoral degrees in the health professions or in a health-related science. RCMI institu­tions also conduct research on diseases that disproportionately affect racial and ethnic minorities (ie, African Americans/Blacks, American Indians and Alaska Natives, His­panics, Native Hawaiians and Other Pacific Islanders), those of low socioeconomic sta­tus, and rural persons. Quantitative metrics, including the numbers of doctoral science degrees granted to underrepresented stu­dents, NIH peer-reviewed research funding, peer-reviewed publications, and numbers of racial and ethnic minorities participat­ing in sponsored research, demonstrate that RCMI grantee institutions have made substantial progress toward the intent of the Congressional legislation, as well as the NIH/NIMHD-linked goals of addressing workforce diversity and health disparities. Despite this progress, nationally, many challenges remain, including persistent disparities in research and career develop­ment awards to minority investigators. The continuing underrepresentation of minority investigators in NIH-sponsored research across multiple disease areas is of concern, in the face of unrelenting national health inequities. With the collaborative network support by the RCMI Translational Research Network (RTRN), the RCMI community is uniquely positioned to address these chal­lenges through its community engagement and strategic partnerships with non-RCMI institutions. Funding agencies can play an important role by incentivizing such col­laborations, and incorporating metrics for research funding that address underrep­resented populations, workforce diversity and health equity.Ethn Dis. 2019;29(Suppl 1):135-144; doi:10.18865/ed.29.S1.135.