703-THE INDIRECT ACTION OF IONS UPON AMINO ACID TRANSPORT SYSTEM L IN THE S37 CELL

The uptake into S37 ascites cells of an L-system specific analog, 2-amino-bicycle-(3,2,1)-octanecarbo xylic acid (ABOCA), was inconsistently inhibited by deletion of sodium ion from the incubation medium. We note that there have been conflicting reports from various other laboratories as to the effect of sodium ion on the transport of L-system specific analogs. The uptake of labeled exo-2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) was also diminished by the removal of sodium from the medium. The K,, values for these substrates were increased and vmax values decreased as the sodium ion concentration was decreased or abolished. Transport behavior was also found to be affected by varying the medium potassium ion concentration with valinomycin present. The sodium effect was abolished by preincubation with cyanide and deoxyglucose. The results suggest an indirect effect of sodium ion upon transport system L: system L is energetically supported by a membrane potential