A novel technique for identification of sites of anion transport in intact cells and tissues using a fluorescent probe

Abstract The purported blocker of anion transport 4, 4′ di-isothiocyano-2-2′ stilbene disulfonate (DIDS) has been shown to partially inhibit ³⁶Cl^? influx, ³⁶CIO^?₃ influx and ³⁵SO^2?₄ influx into Pisum salivum L. cv. Feltham First seedlings. This inhibitory effect could be prevented by pretreatment with the respective unlabelled medium. There was no effect of DIDS on ¹⁴C methylamine influx. The results are consistent with the hypothesis that the binding of DIDS to the site of anion-carrier interaction is responsible for its observed inhibitory effects on anion fluxes. The fluorescent properties of DIDS upon binding to membrane proteins was exploited in an attempt to examine the major sites of anion pumping in whole roots. The results show clearly that in the presence of DIDS the epidermal layers became brightly fluorescent, while cortical layers did not fiuoresce. Lycopersicum esculentum cells taken from locular fluid were plasmolysed using sucrose solution, and the patterns of fluorescence in the presence of DIDS showed in an unambiguous way that the fluorescence is associated with cell membranes. The potential usefulness of this technique to probe sites of anion transport in whole plants and tissues is discussed.