The permeation of human red cells by 4,6-O-ethylidene- -D-glucopyranose (ethylidene glucose).

1. The glucose derivative 4, 6-O-ethylidene-alpha-D-glucopyranose (ethylidene glucose) was found to inhibit glucose exit competitively but its penetration into human red cells was unaffected by glucose in the medium.2. In penetrating red cells ethylidene glucose followed diffusion type kinetics without any evidence of saturation up to 360 mM. Besides its penetration being unaffected by glucose, 10(-5)M phloretin, which powerfully inhibits the facilitated transfer of hexoses, did not inhibit penetration.3. Red cells incubated with 1-fluoro-2, 4-dinitrobenzene (FDNB) until glucose exit was reduced by 95% showed no slowing of penetration by ethylidene glucose.4. The potentiation of the development of FDNB inhibition by sugars in the incubating medium was absent when ethylidene glucose was used and there was a slight protective action. Cells pre-incubated with 76 mM ethylidene glucose did not show an uphill transfer from 4 mM-[(14)C]glucose in the outside medium in contrast to cells pre-incubated in 76 mM glucose or in 76 mM 3-O-methyl glucose.5. The possibility that ethylidene glucose penetrated human red cells by simple diffusion was supported by its penetration of guinea-pig red cells at similar rates, by the occurrence of osmotic haemolysis in isosmotic solutions which was unaffected by copper ions and by the relatively high ether/water partition of the compound.