Properties of the bursting Na channel in the presence of DPI 201-106 in guinea-pig ventricular myocytes.
Single Na channel currents were measured in cell-attached patches of guinea-pig ventricular myocytes in the presence of the S-enantiomer of DPI 201-106. DPI changes the kinetic pattern of channel activity from short living openings at the beginning of a depolarizing pulse (voltage-independent mean open time about 0.4 ms between -60 and -20 mV), into longlasting burst of openings. The single channel current-voltage relation can be approximated by a straight line with a single channel conductance of 15 pS, which is the same as in the absence of DPI, and a reversal potential near the estimated Na equilibrium potential (+74 mV). The ensemble averaged Na current shows a fast peak of inward current, which partially decays within less than 10 ms, but which shows a large component which decays very slowly with a time constant of the order of 1 s (1.31 +/- 0.6 s at -30 mV, 19 measurements in 12 cell-attached patches). The slowly decaying component activates with a half-maximum potential at -55.4 +/- 2.3 mV and a slope parameter s of 4.9 +/- 1.9 mV. The half-maximum potential of the steady-state inactivation is -115.6 +/- 1.8 mV, and the slope parameter is 9.1 +/- 1.5 mV. The open time distribution can be fitted by a single exponential only at potentials negative to -40 mV. The time constant is 1.3 +/- 0.14 ms at -50 mV (7 patches).(ABSTRACT TRUNCATED AT 250 WORDS)
Nilius
B
B
Laboratory of Physiology, Leuven, Belgium.
Vereecke
J
J
Carmeliet
E
E
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects; D006352:Heart Ventricles; D007700:Kinetics; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*
D010879:Piperazines; D015222:Sodium Channels; D002104:Cadmium; C046261:DPI 201-106