title: Hypoxia-induced hyperpolarization is not associated with vasodilation of bovine coronary resistance arteries.
abstract: The effect of reduced PO2 on the transmembrane potential and diameter of small cannulated coronary resistance arteries was evaluated by microelectrode and videomicroscopic methods. Bovine coronary resistance arteries (158 +/- 8 microm ID) were cannulated with glass micropipettes and perfused and superfused with physiological salt solution. Lowering the PO2 of the physiological salt solution from 140 +/- 4 to 36 +/- 2 mmHg increased the smooth muscle cell transmembrane potential from -51 +/- 2 to -62 +/- 2 mV in both endothelium-intact and -denuded coronary resistance arteries. This hyperpolarization was blocked by superfusion with the K+-channel blocker glibenclamide (1 microM). However, low PO2 did not significantly dilate either endothelium-intact or -denuded coronary resistance arteries, although superfusion with 1 microM cromakalim, a K+-channel activator, induced a 6-mV hyperpolarization and increased the diameter by 33 +/- 10 microm. These results suggest that reduced PO2 directly hyperpolarizes the vascular smooth muscle of coronary resistance arteries by activation of glibenclamide-sensitive K+ channels, but other nonvascular mechanisms may mediate the vasodilation response to low PO2.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee 53226, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Gauthier-Rein
authors.forename: D M
authors.initials: DM
authors.lastname: Bizub
authors.forename: J H
authors.initials: JH
authors.lastname: Lombard
authors.forename: N J
authors.initials: NJ
authors.lastname: Rusch
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D019806:Cromakalim; D004730:Endothelium, Vascular / Q000502:physiology*; D005905:Glyburide / Q000494:pharmacology; D000860:Hypoxia; D066298:In Vitro Techniques; D008564:Membrane Potentials; D008839:Microelectrodes; D018715:Microscopy, Video; D010100:Oxygen / Q000097:blood; D010477:Perfusion; D011758:Pyrroles / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D001578:Benzopyrans; D011758:Pyrroles; D014665:Vasodilator Agents; D019806:Cromakalim; D000109:Acetylcholine; D010100:Oxygen; D001920:Bradykinin; D005905:Glyburide; D002118:Calcium