Sugar uptake by protoplasts isolated from suspension cultured cells of Vinca rosea was studied. Several respiratory inhibitors including sodium azide, iodoacetate, and dinitrophenol inhibited D-glucose uptake. The uptake also declined at low temperature. This evidence suggests that the uptake by protoplasts depends on cellular energy. D-Glucose, D-fructose and sucrose showed alkalinization of the medium, suggesting that protons entered into cells together with these sugars. In contrast, sorbitol induced very little alkalinization and inositol as well as dextran showed no alkalinization of the medium. Diethylstilbestrol (DES) and vanadate, an inhibitor of plasmalemma ATPase, depressed the uptake of D-glucose by protoplasts. This suggests the involvement of plasmalemma ATPase in D-glucose-cotransport with protons. Similar inhibition of D-glucose uptake was observed with N,N???-dicyclohexyl carbodiimide (DCCD), an inhibitor of energy transfer, and oligomycin, an inhibitor of mitochondrial ATPase. The presence of KCl weakened the effect of DES, DCCD and vanadate, but not of oligomycin. ?? 1982.
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