Effect of N-ethylmaleimide on leucine transport in Chang liver cells. I. stimulatory effect on Na+ -independent transport at low concentrations of leucine.
Pretreatment of Chang liver cells with N-ethylmaleimide (0.5 or 1 mM) stimulated Na+ -independent uptake of leucine at low concentrations (less than or equal to 1 mM). The stimulatory effect of N-ethylmaleimide on the uptake of leucine measured in Na+ -replete medium was completely blocked by the addition of beta-2-aminobicyclo[2,2,1]heptane-2-carboxylate (5 mM), which shows that the L system participates in the stimulation. The Na+ -dependent uptake of glycine was depressed by N-ethylmaleimide pretreatment. The stimulation of the Na+ -independent component of leucine uptake continued for at least 30 min after N-ethylmaleimide treatment, while the inhibition of glycine uptake was progressive with time and the Na+ -dependent uptake of leucine became depressed later, after the treatment. It has been demonstrated that treatment of cells with N-ethylmaleimide is capable of increasing the Na+ -independent influx of leucine and at the same time slightly decreasing the efflux of it. These results suggest that N-ethylmaleimide attacks the Na+ -independent system of amino acid transport at the reactive SH groups(s) of relevant protein(s) in favor of specific activation of that system in this cell.
D000621:Aminoisobutyric Acids / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002460:Cell Line; D005033:Ethylmaleimide / Q000494:pharmacology*; D005998:Glycine / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*
D000621:Aminoisobutyric Acids; C017911:2-(methylamino)isobutyric acid; D012964:Sodium; D007930:Leucine; D005033:Ethylmaleimide; D005998:Glycine