The indirect action of ions upon amino acid transport system L in the S37 cell

Abstract

The uptake into S37 ascites cells of an L-system specific analog, 2-amino-bicyclo-(3,2,1)-octanecarboxylic acid (ABOCA), wasinconsistently 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) wasalso diminished by the removal of sodium from the medium. The Km values for these substrates were increased and [nu]max 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.