On the nature of permeability of sarcoma-180 cells to amethopterin in vitro

摘要: Abstract The rate of net influx amethopterin into sublines Sarcoma-180 cells in vitro (4.6 · 10 −8 cm/sec at 36°) was shown to be dependent on least four processes: (a) slow influx, apparently by diffusion; (b) rapid, energy-dependent efflux; (c) very rapid binding inhibitor intracellular folic acid reductase (EC 1.5.1.3); and (d) dissociation the latter complex. requires a large activation energy 30.5 kcal which is explained poor lipid solubility negative charge molecule. Influx increased increasing H + -ion concentration, also high concentrations Ca 2+ . Both these are likely decrease ionization two carboxyl groups glutamyl-end molecule thus facilitate their entry through negatively charged cell surface. probably acts forming an [amethopterin-Ca 2 ] chelate. Combination 2,4-dinotrophenol, oxidative phosphorylation, apparent 5–6-fold. Riboflavin, natural ingredient growth medium, folinic were found able partially down amethopterin.