In the brain, pressure-induced myogenic constriction of cerebral arteriolar muscle contributes to autoregulation of cerebral blood flow (CBF). This study examined the role of 20-HETE in autoregulation of CBF in anesthetized rats. The expression of P-450 4A protein and mRNA was localized in isolated cerebral arteriolar muscle of rat by immunocytochemistry and in situ hybridization. The results of reverse transcriptase-polymerase chain reaction studies revealed that rat cerebral microvessels express cytochrome P-450 4A1, 4A2, 4A3, and 4A8 isoforms, some of which catalyze the formation of 20-HETE from arachidonic acid. Cerebral arterial microsomes incubated with [(14)C]arachidonic acid produced 20-HETE. An elevation in transmural pressure from 20 to 140 mm Hg increased 20-HETE concentration by 6-fold in cerebral arteries as measured by gas chromatography/mass spectrometry. In vivo, inhibition of vascular 20-HETE formation with N-methylsulfonyl-12, 12-dibromododec-11-enamide (DDMS), or its vasoconstrictor actions using 15-HETE or 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (20-HEDE), attenuated autoregulation of CBF to elevations of arterial pressure. In vitro application of DDMS, 15-HETE, or 20-HEDE eliminated pressure-induced constriction of rat middle cerebral arteries, and 20-HEDE and 15-HETE blocked the vasoconstriction action of 20-HETE. Taken together, these data suggest an important role for 20-HETE in the autoregulation of CBF.
The present study examined whether inhibition of P4504A enzyme activity and the formation of 20-HETE contributes to the activation of K+ channels and vasodilator effects of nitric oxide (NO) in renal arterioles. Addition of an NO donor to the P4504A2 enzyme that produces 20-HETE increased visible light absorbance at 440 nm indicating that NO binds to heme in this enzyme. NO donors also dose-dependently inhibited the formation of 20-HETE in microsomes prepared from renal arterioles. In patch-clamp experiments, NO donors increased the open-state probability of a voltage-sensitive, large-conductance (195+/-9 pS) K+ channel recorded with cell-attached patches on renal arteriolar smooth muscle cells. Blockade of guanylyl cyclase with [1H-[1,2,4]Oxadiazolo[4,3-a] quinoxalin-1-one] (ODQ, 10 micromol/L), or cGMP-dependent kinase with 8R,9S,11S-(-)-9-methoxycarbamyl-8-methyl-2,3,9,10-tetrahydro-8, 11-epoxy-1H,8H,11H-2,7b,11a-trizadibenzo-(a,g)-cy-cloocta-(c ,d, e)-trinden-1-one (KT-5823) (1 micromol/L) did not alter the effects of NO on this channel. In contrast, inhibition of the formation of 20-HETE with 17-octadecynoic acid (1 micromol/L) activated this channel and masked the response to NO. Preventing the NO-induced reduction in intracellular 20-HETE levels also blocked the effects of NO on this channel. Sodium nitroprusside (SNP) increased the diameter of renal interlobular arteries preconstricted with phenylephrine to 80+/-4% of control. Blockade of guanylyl cyclase with ODQ (10 micromol/L) attenuated the response to SNP by 26+/-2%; however, fixing 20-HETE levels at 100 nmol/L reduced the response by 67+/-8%. Blockade of both pathways eliminated the response to SNP. These results indicate that inhibition of the formation of 20-HETE contributes to the activation of K+ channels and the vasodilator effects of NO in the renal microcirculation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.