Verapamil-induced kinetics of ion flux in oat seedlings

Abstract

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.