Abstract
Renal cyclooxygenase (COX)-2 expression is increased in the streptozotocin (STZ)-diabetic rat and is associated with enhanced renal prostaglandin release in response to arachidonic acid (AA). Endoperoxide-mediated vasoconstrictor responses to AA were also enhanced in the diabetic rat kidney. Because oxidative stress is increased in diabetes and has been shown to induce COX-2, we assessed its contribution to prostaglandin release by treating diabetic rats with tempol (120 mg/kg/day) for 28 days. Release of AA-stimulated prostaglandins PGE2 and 6-ketoPGF1α from the isolated perfused kidney was used as an index of COX activity, and Western analysis was used to determine COX-2 protein expression. In untreated diabetic rats, the release of prostaglandins in response to AA was markedly enhanced; the increase in release of both 6-ketoPGF1α and PGE2 after AA was twice that in control rats. Renal cortical COX-2 expression in diabetic rats was 3-fold that of control rats. Tempol treatment reduced the AA-stimulated release of prostaglandins to levels seen in control rats; this was associated with reduced expression of COX-2 protein to levels not different from that in control rats. However, the enhanced vasoconstrictor response to AA in diabetic rats was unaffected by tempol treatment but abolished by inhibition of COX-1 with SC58560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole]. The addition of tempol to the perfusate of kidneys from diabetic and control rats had only a slight effect on prostaglandin release. We conclude that oxidative stress is an integral component of the mechanism involved in the induction of renal COX-2 in diabetes.
Footnotes
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This work was supported by a grant from the American Diabetes Association and National Institutes of Health Grant HL-069061.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.104.076927.
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ABBREVIATIONS: AA, arachidonic acid; COX, cyclooxygenase; GFR, glomerular filtration rate; STZ, streptozotocin; SC58560, 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole; PG, prostaglandin; U46619, 9,11-dideoxy-9α,11α-methanoepoxy PGF2α.
- Received August 31, 2004.
- Accepted May 5, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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