Sodium-activated potassium current in guinea pig gastric myocytes.
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.
Kim
Young Chul
YC
Department of Physiology, Chungbuk National University, College of Medicine, Cheongju, Korea. physiokyc@chungbuk.ac.kr
Sim
Jae Hoon
JH
Kang
Tong Mook
TM
Suzuki
Hikaru
H
Kim
Seung Ryul
SR
Kwon
Seong-Chun
SC
Xu
Wen-Xie
WX
Lee
Sang Jin
SJ
Kim
Ki Whan
KW
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
D002712:Chlorides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D012964:Sodium; D002118:Calcium