Submitted on May 19, 2003
Accepted on July 8, 2003
Reactive Oxygen Species Mediate Arachidonic Acid - Induced Dilation in Porcine Coronary Microvessels
Christine L. Oltman1*, Neal L. Kane2, Francis J. Miller3, Arthur A. Spector4, Neal L. Weintraub5, and Kevin C. Dellsperger1
1 Department of Internal Medicine and the Cardiovascular Center, University of Iowa, Iowa City, Iowa, USA; Department of Veterans Affairs, University of Iowa, Iowa City, Iowa, USA
2 Department of Internal Medicine and the Cardiovascular Center, University of Iowa, Iowa City, Iowa, USA
3 Department of Internal Medicine and the Cardiovascular Center, University of Iowa, Iowa City, Iowa, USA; the Free Radical and Radiation Biology Program, University of Iowa, Iowa City, Iowa, USA
4 Department of Internal Medicine and the Cardiovascular Center, University of Iowa, Iowa City, Iowa, USA; Department of Biochemistry, Univerity of Iowa, College of Medicine, Iowa City, Iowa, USA
5 Department of Internal Medicine and the Cardiovascular Center, University of Iowa, Iowa City, Iowa, USA; Department of Veterans Affairs, University of Iowa, Iowa City, Iowa, USA; the Free Radical and Radiation Biology Program, University of Iowa, Iowa City, Iowa, USA
* To whom correspondence should be addressed. E-mail: christine-oltman{at}uiowa.edu.
Reactive oxygen species (ROS) have been proposed to mediate vasodilation in the microcirculation. We investigated the role of ROS in arachidonic acid (AA)-induced coronary microvascular dilation. Porcine epicardial coronary arterioles (110 ± 4 µm diameter) were mounted onto pipettes in oxygenated Kreb's buffer. Vessels were incubated with vehicle or 1mM Tiron (a non-selective ROS scavenger), 250 units/ml polyethylene-glycolated (PEG)-superoxide dismutase (SOD, a O2.- scavenger), 250 units/ml PEG-catalase (a H2O2 scavenger), or the cyclooxygenase (COX) inhibitors indomethacin (10 µM) or diclofenac (10 µM) for 30 min. After endothelin constriction (30-60 % of resting diameter), cumulative concentrations of AA (10- 10 to 10-5 M) were added and internal diameters measured by video microscopy. Results: AA (10-7 M) produced 37 ± 6% dilation, which was eliminated by administration of indomethacin [4 ± 7%, p<0.05]or diclofenac [-8 ± 8%, p<0.05], as well as by Tiron [-4±5%, p<0.05], PEG-SOD [-10 ± 6%, p<0.05], or PEG-catalase [1 ± 4%, p<0.05]. Incubation of small coronary arteries with [3H]AA resulted in formation of prostaglandins, which was blocked by indomethacin. In separate studies in microvessels, AA induced concentration-dependent increases in fluorescence of the oxidant-sensitive probe dichlorodihydrofluorescein diacetate, which was inhibited by pretreatment with indomethacin or by SOD + catalase. We conclude that in porcine coronary microvessels, COX-derived ROS contribute to AA-induced vasodilation.
