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.