The influence of phenylephrine outward potassium currents in single smooth muscle cells from the rabbit mesenteric artery.
In mesenteric artery smooth muscle cells, depolarizing voltage steps activated outward K+ currents whose amplitude was decreased by about 20% with phenylephrine (1-10 microM: n = 14 cells). Attenuation of outward current was only partly dependent on [Ca2+]i, because it persisted, although reduced, with 10 mM BAPTA in the patch pipette and was abolished in the presence of 3 mM 3,4-diaminopyridine (n = 13). In outside-out patches, phenylephrine did not exert any direct effect on the unitary current amplitude or open probability of large conductance K+ channels. Outward current was significantly increased (>100% in both cases) by 10 mM caffeine, presumably owing to the release of internal Ca2+ stores. With 10 mM BAPTA in the pipette, the only response to caffeine was a small decrease (9 +/- 3.7%, n = 10) in the K+ current. These observations show that a minor effect of phenylephrine is to reduce outward K+ current (probably Kv) in mesenteric cells.
Mistry
D K
DK
Department of Pharmacology, University of Bristol, UK.
Garland
C J
CJ
D015761:4-Aminopyridine / Q000031:analogs & derivatives / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000077770:Amifampridine; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D004347:Drug Interactions; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D019789:Tetraethylammonium / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D002614:Chelating Agents; D015221:Potassium Channels; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D002110:Caffeine; D004533:Egtazic Acid; D019789:Tetraethylammonium; D015761:4-Aminopyridine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D000077770:Amifampridine; D011188:Potassium; D002118:Calcium; D011224:Prazosin