Further observations on the inhibitory effect of extracellular potassium ions on glycine uptake by mouse ascites-tumour cells
- 1 October 1969
- journal article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 114 (4), 807-814
- https://doi.org/10.1042/bj1140807
Abstract
1. The initial rate of uptake of glycine by the tumour cells was measured as a function of the Na+ and K+ concentrations in the solution in which the cells were suspended. When [Gly] was 1mm or 12mm, the rate in the absence of Na+ was independent of [K+] and about 3% or 10% respectively of the rate when [Na+] was 150m-equiv./l. 2. The Na+-dependent glycine entry rate, v, at a given value of [Na+] was successively lowered when [K+] was increased from 8 to 47 to 96m-equiv./l. A kinetic analysis indicated that K+ competitively inhibited the action of Na+. The results were in fair agreement with previous determinations of the kinetic parameters. 3. The presence of 2mm-sodium cyanide and 10mm-2-deoxyglucose lowered the cellular ATP content to less than 3% of the value in the respiring cells. Although v was then about 50% smaller, the relative effects of K+ and Na+ on the system were similar to those observed during respiration. 4. A theoretical analysis indicated that the variation of v with [K+] is not a reliable guide to the extent to which the K+ gradient between the cells and their environment may contribute to the net transport of glycine.Keywords
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