Peroxynitrite inhibits Ca2+-activated K+ channel activity in smooth muscle of human coronary arterioles.
We examined the hypothesis that ONOO-, a product of the interaction between superoxide (O2*-) and nitric oxide (NO), inhibits calcium-activated K+ (KCa) channel activity in vascular smooth muscle cells (VSMCs) of human coronary arterioles (HCAs), thereby reducing hyperpolarization-mediated vasodilation. HCAs were dissected from right atrial appendages. The interaction of ONOO- with microvessels was determined by immunohistochemistry using a nitrotyrosine antibody. Strong staining was observed in arteries exposed to authentic ONOO- or to sodium nitroprusside (SNP)+xanthine (XA)+xanthine oxidase (XO). Dilation to 10(-8) mol/L bradykinin (BK) was abolished in vessels exposed to ONOO- (-2.5+/-8%; P<0.05) but not DC-ONOO- (65+/-8%). Reduced dilation to BK was also observed after application of XO and SNP. Dilation to NS1619 (KCa channel opener) was reduced in endothelial denuded arterioles treated with ONOO-. In isolated VSMCs, whole-cell peak K+ current density was reduced by ONOO- (control 65+/-15 pA/pF; ONOO- 42+/-9 pA/pF; P<0.05). Iberiotoxin had no further effect on whole-cell K+ current. In inside-out patches, ONOO- but not DC-ONOO- decreased open state probability (NP(o)) of KCa channel by 50+/-12%. O2*- generated by XA+XO had no effect on BK-induced dilation and NP(o) of KCa channels. These results suggest that ONOO-, but not O2*-, inhibits KCa channel activity in VSMCs possibly by a direct effect. This mechanism may contribute to impaired EDHF-mediated dilation in conditions such as ischemia/reperfusion where increased activity of NO synthase occurs in the presence of excess of O2*-.
Liu
Yanping
Y
Department of Internal Medicine, Medical College of Wisconsin, and Zablocki VA Medical Center, Milwaukee, Wis 53226, USA. ypliu@mcw.edu
Terata
Ken
K
Chai
Qiang
Q
Li
Hongwei
H
Kleinman
Leonard H
LH
Gutterman
David D
DD
D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism*; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018715:Microscopy, Video; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D030421:Peroxynitrous Acid / Q000096:biosynthesis / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000096:biosynthesis; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
D010455:Peptides; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D014665:Vasodilator Agents; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; C064719:iberiotoxin; D011188:Potassium