LANTHANUM BLOCKS A SPECIFIC COMPONENT OF IK AND SCREENS MEMBRANE-SURFACE CHARGE IN CARDIAC-CELLS

被引:78
作者
SANGUINETTI, MC
JURKIEWICZ, NK
机构
来源
AMERICAN JOURNAL OF PHYSIOLOGY | 1990年 / 259卷 / 06期
关键词
DELAYED RECTIFIER; POTASSIUM ION CURRENT; GUINEA PIG; MYOCYTES;
D O I
10.1152/ajpheart.1990.259.6.H1881
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Delayed rectifier outward K+ current (I(K)) in guinea pig ventricular myocytes represents the sum of two currents: a slowly activating delayed rectifier K+ current (I(K,s)) and a relatively rapidly activating delayed rectifier K+ current (I(K,r)) which rectifies at positive potentials and is specifically blocked by the class III antiarrhythmic agent, E-4031. La3+ was previously reported to block an unidentified component of I(K) in these cells. We used the whole cell voltage-clamp technique on isolated myocytes and confirmed these results; we show that the current blocked by La3+ (greater-than-or-equal-to 1-mu-M) is I(K,r). This block is not caused by La3+ displacement of surface-bound Ca2+. Thus, in the presence of either E-4031 or La3+, I(K) represents the activation of a single current, I(K,s). La3+ (10-mu-M-1 mM) also caused a positive shift in the voltage dependence of the activation curve of I(K,s). When we assumed that La3+ acts to bind and screen negative surface charges on the outer sarcolemmal membrane, the external surface potential of these cells (in 1.8 mM Ca2+) could be estimated to be -19 mV. A modification of the Gouy-Chapman equation was used to estimate the equilibrium constant for La3+ binding (10.7 mM-1) and the minimum spacing between the negative charges on the surface membrane (22 angstrom).
引用
收藏
页码:H1881 / H1889
页数:9
相关论文
共 25 条
[1]   EXTERNAL CALCIUM-IONS ARE REQUIRED FOR POTASSIUM CHANNEL GATING IN SQUID NEURONS [J].
ARMSTRONG, CM ;
LOPEZBARNEO, J .
SCIENCE, 1987, 236 (4802) :712-714
[2]  
BALSER JR, 1988, BIOPHYS J, V53, pA642
[3]  
BALSER JR, IN PRESS J GEN PHYSL
[4]   ACTION OF CERTAIN POLYVALENT CATIONS ON VOLTAGE-CLAMPED LOBSTER AXON [J].
BLAUSTEI.MP ;
GOLDMAN, DE .
JOURNAL OF GENERAL PHYSIOLOGY, 1968, 51 (03) :279-&
[5]   DISPLACEMENT OF ACTIVATION THRESHOLDS IN CARDIAC-MUSCLE BY PROTONS AND CALCIUM-IONS [J].
BROWN, RH ;
NOBLE, D .
JOURNAL OF PHYSIOLOGY-LONDON, 1978, 282 (SEP) :333-343
[6]   EFFECTS OF CALCIUM ON OUTWARD MEMBRANE CURRENTS IN THE CARDIAC PURKINJE-FIBER [J].
DIFRANCESCO, D ;
MCNAUGHTON, PA .
JOURNAL OF PHYSIOLOGY-LONDON, 1979, 289 (APR) :347-373
[7]  
GILBERT DL, 1971, BIOPHYSICS PHYSL EXC, P359
[8]   VOLTAGE CLAMP OF BULL-FROG CARDIAC PACE-MAKER CELLS - A QUANTITATIVE-ANALYSIS OF POTASSIUM CURRENTS [J].
GILES, WR ;
SHIBATA, EF .
JOURNAL OF PHYSIOLOGY-LONDON, 1985, 368 (NOV) :265-&
[9]   COMPARISON OF POTASSIUM CURRENTS IN RABBIT ATRIAL AND VENTRICULAR CELLS [J].
GILES, WR ;
IMAIZUMI, Y .
JOURNAL OF PHYSIOLOGY-LONDON, 1988, 405 :123-145
[10]   NEGATIVE SURFACE CHARGE NEAR SODIUM CHANNELS OF NERVE - DIVALENT IONS, MONOVALENT IONS, AND PH [J].
HILLE, B ;
WOODHULL, AM ;
SHAPIRO, BI .
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, 1975, 270 (908) :301-318