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 Ca2+, 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 tetraethylammonium, Cs+, Ba2+ or Ca2+ did not affect K+ flux changes, whereas DMSO, Cd2+ 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 Ca2+ flux to efflux. Pre-treatment with adrenaline and dopamine agonists and antagonists led to changes in verapamil-induced ion flux, especially for Ca2+. We suggest that a transporter that allows entry of K+ and Na+ was the main system providing monovalent ion influx after verapamil application.