cells utilize arginine via the arginine dihydrolase pathway. L-Arginine uptake by intact cells was a saturable process both as a function of time and arginine concentration ( = 40 μM). Uptake was not affected by pH in the range pH 5.0-8.0, or by L-citrulline, D-arginine, L-histidine or L-canavanine at concentrations tenfold higher than that of L-arginine. In contrast, L-arginine uptake was markedly inhibited by L-ornithine and partially inhibited by L-lysine. Uptake was neither affected by protonophores nor by cation ionophores, but was inhibited by protease treatment or by the sulfhydryl reagents -chloromercuribenzoate or -ethylmaleimide. Sealed membrane vesicles prepared by fusing isolated membranes with asolectin-cholesterol vesicles catalysed a rapid exchange (t = 1 min) between arginine and ornithine. Exchange did not require ATP and could be demonstrated in both directions, i.e. with either arginine or ornithine trapped within vesicles. These observations suggest that the driving forces for arginine uptake by whole cells are the concentration gradients of arginine and ornithine formed by arginine metabolism.


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