Collateral response to activation of potassium channels in vivo.
Activation of ATP-sensitive K+ channels is involved in the coronary vascular response to decreases in perfusion pressure and ischemia. Since activation of ATP-sensitive K+ channels in collateral vessels may be important in determining flow to collateral-dependent myocardium, the ability of collaterals to respond to activation of the channel was tested. In the beating heart of dogs, we compared responses of non-collaterals less than 100 microns in diameter to collaterals of similar size using computer-controlled stroboscopic epi-illumination of the left ventricle coupled to a microscope-video system. Aprikalim, a selective activator of ATP-sensitive K+ channels (0.1-10 microM) produced similar dose-dependent dilation of non-collaterals and collaterals. Relaxation was decreased by inhibition of ATP-sensitive K+ channels with glibenclamide, but not by inhibition of nitric oxide synthase with nitro-L-arginine. Bradykinin (10-100 microM) produced similar dilation of non-collaterals and collaterals which was decreased by nitro-L-arginine but not glibenclamide. Thus, in microvascular collaterals, relaxation to both nitric oxide and activation of ATP-sensitive K+ channels is similar to non-collaterals.
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Medical Services (111), VA Medical Center, Iowa City 52246, USA. kathryn-lamping@uiowa.edu
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000008:administration & dosage / Q000494:pharmacology; D003097:Collateral Circulation / Q000187:drug effects*; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000187:drug effects*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D008833:Microcirculation / Q000033:anatomy & histology / Q000187:drug effects*; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010847:Picolines / Q000008:administration & dosage / Q000494:pharmacology*; D015221:Potassium Channels / Q000502:physiology*; D011714:Pyrans / Q000008:administration & dosage / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D010847:Picolines; D015221:Potassium Channels; D011714:Pyrans; D014665:Vasodilator Agents; D009599:Nitroprusside; D019335:Nitroarginine; C061043:aprikalim; D000109:Acetylcholine; D001920:Bradykinin; D005905:Glyburide