[Effect of oxyphenamone on sodium and calcium channels of guinea pig myocardial cells].
OBJECTIVE
To investigate the mechanism of the positive inotropic effect of oxyphenamone.


METHODS
With the patch clamp technique and whole cell recording, the sodium and L type calcium currents of myocytes isolated from ventricular myocardium of adult guinea pigs were studied.


RESULTS
5 - 50 micromol x L(-1)-oxyphenamone not only significantly inhibited Na+ current, but also promoted the process of inactivation and prolonged the recovery time of the inactivation. The action of oxyphenamone on L type calcium channel was dual. The inward calcium current was increased with 2 - 10 micromol x L(-1) oxyphenamone but decreased when the concentration of the drug was elevated to 20 - 50 micromol x L(-1).


CONCLUSIONS
The mechanism of the positive inotropic effect of oxyphenamone is neither due to the activation of sodium channel nor entirely depending upon the activation of L type calcium channel. The effects of inhibiting sodium current and, at a high concentration, blocking L type calcium current suggest that oxyphenamone may have an antiarrhythemia action.
Fan
Li-li
LL
Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China. fanlili@public3.bta.net.cn
Song
Zhen
Z
Wang
Tian-you
TY
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects*; D009930:Organic Chemicals; D018408:Patch-Clamp Techniques; D015222:Sodium Channels / Q000187:drug effects*
D000889:Anti-Arrhythmia Agents; D020746:Calcium Channels, L-Type; D002316:Cardiotonic Agents; D009930:Organic Chemicals; D015222:Sodium Channels; C442156:oxyphenamone