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1 Department of Pharmacology, New York Medical College, Valhalla, New York, USA
2 Department of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
* To whom correspondence should be addressed. E-mail: fan_zhang{at}nymc.edu.
Cytochrome P450-4A1 (CYP4A1) is an 
-hydroxylase which catalyzes metabolism of arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE). The goal of this study was to determine the vasomotor consequences of vascular overexpression of CYP4A1. Isolated rat gracilis muscle arterioles transfected ex vivo with an expression plasmid containing CYP4A1 cDNA expressed more CYP4A protein
than vessels transfected with the control plasmid. In arterioles pressurized to 80 mmHg, the internal diameter of vessels transfected with CYP4A1 cDNA (55±3 µm) was surpassed (P<0.05) by that of vessels transfected with control plasmid (97±4 µm). Treatment with a CYP4A inhibitor (N-methylsulfonyl-12, 12-dibromododec-11-enamide; DDMS), or with an antagonist of 20-HETE actions (20-hydroxyeicosa-6 (Z),15(Z)- dienoic acid; 20-HEDE), elicited robust dilation of arterioles transfected with CYP4A1 cDNA while having little or no effect in vessels transfected with control plasmid.
Examination of the intraluminal pressure-internal diameter relationship revealed that pressure increments over the range 40-100 mmHg elicited a more intense (P<0.05)
myogenic constrictor response in arterioles transfected with CYP4A1 cDNA than with control plasmid. Arterioles transfected with CYP4A1 cDNA also displayed enhanced
sensitivity to the constrictor action of phenylephrine. Treatment with DDMS or 20-HEDE greatly attenuated the constrictor responsiveness to both constrictor stimuli in vessels overexpressing CYP4A1 while having much less effect in control vessels. These data suggest that CYP4A1 overexpression promotes constriction of gracilis muscle arterioles by intensifying the responsiveness of vascular smooth muscle to constrictor stimuli. This effect of CYP4A1 overexpression appears to be mediated by a CYP4A1 product.
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