[Effect of KB-R7943 on Na(+)-Ca2+ exchange current in guinea pig ventricular myocytes].
OBJECTIVE
To study whether KB-R7943 has selective inhibitory effect on the inward and outward Na(+)-Ca2+ exchange current (INa-Ca) in guinea pig ventricular myocytes.


METHODS
Through setting up the model of intracellular Na(+)-overload during myocardial ischemia and reperfusion, the current-voltage relationship of INa-Ca was recorded using whole-cell patch clamp technique under bi-directional ionic conditions.


RESULTS
Currents were elicited by a declining ramp pulse depolarized immediately from holding potential of -40 mV to +60 mV, then repolarized to -100 mV at a speed of 80 mV.s-1 and returned to the holding potential under bi-directional ionic conditions, while the [Na+] was 25 mmol.L-1 in the pipette solution. The currents increased time-dependently and voltage-dependently which reached from (2.51 +/- 0.15) pA.pF-1 to (5.94 +/- 0.13) pA.pF-1 at  mV and from (-1.92 +/- 0.13) pA.pF-1 to (-3.17 +/- 0.16) pA.pF-1 at -80 mV (n = 12) after 3 min and there is no significant run-down of the current. KB-R7943 10(-6) mol.L-1 was found to decrease the current to (4.62 +/- 0.05) pA.pF-1 by 29.4% at  mV and to (-2.30 +/- 0.18) pA.pF-1 by 22.1% at -80 mV (n = 5) after 5 min. While 10(-5) mol.L-1 KB-R7943 was shown to decrease the current to (3.13 +/- 0.03) pA.pF-1 by 61.7% at  mV and to (-1.62 +/- 0.03) pA.pF-1 by 56.9% at -80 mV (n = 7).


CONCLUSIONS
KB-R7943 can block INa-Ca in guinea pig ventricular myocytes. But, it did not show selective inhibition effect on inward and outward currents.
Lu
J
J
Institute of Materia Medica, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100050, China.
Xu
X H
XH
Wang
X L
XL
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D006168:Guinea Pigs; D006352:Heart Ventricles; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D019831:Sodium-Calcium Exchanger / Q000187:drug effects*; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology*
C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; D000889:Anti-Arrhythmia Agents; D019831:Sodium-Calcium Exchanger; D013890:Thiourea