The entrapment of [14C]ascorbic acid in human erythrocytes.

Radioactively labelled ascorbic acid and dehydroascorbic acid, when incubated with human blood, migrate irreversibly into human red blood cells. Isolation and characterization of the moieties trapped within the cells via infrared spectroscopy established both their identities as L-ascorbic acid. Evidence in the form of the degree of in vitro entrapment of ascorbic acid as a function of the times of incubation and the effect of incubation temperature, anion recognition site inhibitor, and active transport inhibitor on the rate of entrapment support the hypothesis that ascorbic acid is oxidized on or near the surface of the red blood cell to dehydroascorbic acid which migrates through the lipid portion of the cell wall and is reduced back to ascorbic acid within the cell. The resulting L-ascorbic acid can not pass through the cell wall and is therefore entrapped.

Benzylpenicillin migrates irreversibly into human erythrocytes.

Benzylpenicillin, 5.2% 14C-enriched, was incubated with human whole blood. The erythrocyte component was washed and exhaustively dialyzed and found to contain 6.3% of the original radioactivity. None of the penicillin was found to bind to the cell membrane. Dialysis of the cell contents indicated that none of the penicillin binds irreversibly to the proteins within the cell. Infrared examination of the contents of the cell leads to the conclusion that benzylpenicillin (a monovalent anion) enters the erythrocyte and is hydrolyzed to benzylpenicilloic acid (a divalent anion). This structural change prevents the antibiotic from migrating out of the cell.