title: On the apparent absence of maxi-K+ channel in rat aortic myocyte.
abstract: In cultured rat aortic myocytes, no high-conductance Ca(2+)-and voltage-dependent K+ channels (maxi-K+ channels) such as those found in the human and rabbit were observed. However, we have found that in freshly dissociated rat aortic myocytes, the activities of high-conductance Ca(2+)-and voltage-dependent channels were present and predominant. In cell-attached patches measured with pipettes filled with normal saline solution, their single channel conductances were 139.6 +/- 2.5 picosiemens (mean +/- SE). Under the 140-mM symmetrical K+ condition (both bath and pipette solutions contained 140 mM KCl), that measurement became 207.2 +/- 3.6 picosiemens and increased by about 50% with detaching of the membrane patch. The relative conductances of the channel to K+, NH4+, and Rb+ were 1:0.61:0.48. The conductance of these channels can readily be reduced by more than 90% by extracellularly applied 0.5 mM tetraethylammonium chloride. These characteristics show that they were maxi-K+ channels.
authors.affiliation: Department of Physiology and Biophysics, State University of New York, Stony Brook 11794.
authors.forename: S F
authors.initials: SF
authors.lastname: Fan
authors.forename: C Y
authors.initials: CY
authors.lastname: Kao
mesh_terms: D000641:Ammonia / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011336:Probability; D051381:Rats; D012413:Rubidium / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D000641:Ammonia; D012413:Rubidium; D011188:Potassium; D002118:Calcium