Verapamil-induced kinetics of ion flux in oat seedlings

Verapamil application in ion transport studies on plant cells is widespread; however, the mechanism of its action is still poorly understood. Net flux of Ca 2+ , K + , Na + , H + and Cl – were measured in solution around oat seedlings using the non-invasive ion-selective microelectrode MIFE technique. The verapamil effect on intact plant tissues was a distinct immediate influx of monovalent cations, H + , K + or Na + . Pre-treatment with tetraethyl-ammonium, Cs + , Ba 2+ or Ca 2+ did not affect K + flux changes, whereas DMSO, Cd 2+ and vanadate increased verapamil-induced K + influx. Verapamil-induced K + flux increased with increased external KCl concentration or pH. Verapamil concentration up to 1 mM failed to shift Ca 2+ flux to efflux. Pre-treatment with adrenaline and dopamine agonists and antagonists led to changes in verapamil-induced ion flux, especially for Ca 2+ . We suggest that a transporter that allows entry of K + and Na + was the main system providing monovalent ion influx after verapamil application.