title: Sodium-activated potassium current in guinea pig gastric myocytes.
abstract: This study was designed to identify and characterize Na+-activated K+ current (I(K(Na))) in guinea pig gastric myocytes under whole-cell patch clamp. After whole-cell configuration was established under 110 mM intracellular Na+ concentration ([Na+]i) at holding potential of -60 mV, a large inward current was produced by external 60 mM K+([K+]degrees). This inward current was not affected by removal of external Ca2+. K+ channel blockers had little effects on the current (p>0.05). Only TEA (5 mM) inhibited steady-state current to 68+/-2.7% of the control (p<0.05). In the presence of K+ channel blocker cocktail (mixture of Ba2+, glibenclamide, 4-AP, apamin, quinidine and TEA), a large inward current was activated. However, the amplitude of the steady-state current produced under [K+]degrees (140 mM) was significantly smaller when Na+ in pipette solution was replaced with K+- and Li+ in the presence of K+ channel blocker cocktail than under 110 mM [Na+]i. In the presence of K+ channel blocker cocktail under low Cl- pipette solution, this current was still activated and seemed K+-selective, since reversal potentials (E(rev)) of various concentrations of [K+]degrees-induced current in current/voltage (I/V) relationship were nearly identical to expected values. R-56865 (10-20 microM), a blocker of I(K(Na)), completely and reversibly inhibited this current. The characteristics of the current coincide with those of I(K(Na)) of other cells. Our results indicate the presence of I(K(Na)) in guinea pig gastric myocytes.
authors.affiliation: Department of Physiology, Chungbuk National University, College of Medicine, Cheongju, Korea. physiokyc@chungbuk.ac.kr
authors.forename: Young Chul
authors.initials: YC
authors.lastname: Kim
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Sim
authors.forename: Tong Mook
authors.initials: TM
authors.lastname: Kang
authors.forename: Hikaru
authors.initials: H
authors.lastname: Suzuki
authors.forename: Seung Ryul
authors.initials: SR
authors.lastname: Kim
authors.forename: Seong-Chun
authors.initials: SC
authors.lastname: Kwon
authors.forename: Wen-Xie
authors.initials: WX
authors.lastname: Xu
authors.forename: Sang Jin
authors.initials: SJ
authors.lastname: Lee
authors.forename: Ki Whan
authors.initials: KW
authors.lastname: Kim
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D008297:Male; D008564:Membrane Potentials; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*; D013270:Stomach / Q000502:physiology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D002712:Chlorides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D012964:Sodium; D002118:Calcium