Ascorbate uptake by isolated rat lung cells.
Experiments were done to determine the intracellular concentration of ascorbate in isolated rat lung cells and the concentration in plasma and to study ascorbate influx in these cells. The intracellular ascorbate concentration was 2.25 mM and the plasma level was about 0.14 mM; i.e., the lung cell ascorbate concentration was about 16 times greater than the plasma level. When the cells were incubated in medium containing physiological levels of ascorbate (0.1 mM), influx increased linearly up to 60 min of incubation and was 0.54 +/- 0.04 nmol.10(7) cells-1.h-1. Influx was dependent on the extracellular ascorbate concentration. At concentrations ranging from 0.025 to 1 mM, uptake appeared to exhibit saturation kinetics with an apparent Km of 0.16 mM. At physiological levels of extracellular ascorbate (0.1 mM) at least 90% of the uptake appeared to be carrier mediated, and this influx was inhibited by various metabolic inhibitors. In addition, ascorbate influx was inhibited by ouabain and removal of extracellular sodium. These results suggest that lung cells contain a transport mechanism for ascorbate that is energy-dependent and that may be coupled to Na+ influx.
D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D001205:Ascorbic Acid / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D008168:Lung / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D012966:Sodium Cyanide / Q000494:pharmacology; D013997:Time Factors
D000963:Antimetabolites; D010042:Ouabain; D012964:Sodium; D012966:Sodium Cyanide; D001205:Ascorbic Acid