Inhibition of Tonoplast and Plasma Membrane H$-ATPase Activity in Rice (Oryza sativa L.) Culture Cells by Local Anesthetics

Tonoplast and plasma membrane vesicles were prepared from rice(Oryza sativa L. var. Yuukara) culture cells with step sucrosegradient (30% and 42.9%, w/v) and/or step dextran T-70 gradient(1% and 8%, w/w) to determine the inhibition of tonoplast andplasma membrane AT-Pases by local anesthetics. The degree towhich the anesthetics inhibited these ATPases was of the followingorder: dibucaine>lidocainetetracaine>procaineGABA. Dibucaineranging in concentration from 0.2 nui to 2 mM inhibited tonoplastATPase activity more than plasma membrane ATPase, the half inhibitionsbeing 0.8 and 1.1 mM, respectively. The K_m values of tonoplastand plasma membrane ATPases were not affected by dibucaine,but various values were noted for V_max. Dibucaine inhibitedtonoplast and plasma membrane ATPases solubilized from 0.1%DOC pellet by n-octylglucoside and zwittergent 3–14, respectively.The addition of a phospholipid mixture (asolectin) to solubilizedboth ATPases had no effect on the inhibition by dibucaine. Thus,local anesthetics may act directly on the ATPase moiety withoutlipid mediation. (Received June 15, 1987; Accepted November 13, 1987)