Abstract
The uptake and efflux of salicylic-714C acid were studied under various incubation and washout conditions. The 60-minute 14C-salicylic acid space at an extracellular pH (pHe) of 7.40 was 1.09 ± 0.037 (S.E.) ml/gm. Elevation on depression of pHe brought about a significant decrease or increase in the 14C-salicylic acid space, respectively. In all cases the observed intracellular/extracellular ratios were greater than those calculated with the intracellular pH determined by 5,5-dimethyloxazolidine-2,4-dione-214C distribution. CN-, 10--5M, or 5° did not affect the 60-minute spaces, whereas decreasing the extracellular concentration from 2.0 to 0.02 mM salicylic acid significantly increased the observed space. Varying the pH in efflux experiments caused an apparent increase in rate at pHe = 8.00 only when the tissue content of radiocarbon had fallen to 20% of its original value. Elevation or depression of pHe after efflux was under way caused a slight increase or decrease in efflux rate respectively. The addition of 2.0 mM nonradioactive salicylic acid to the medium after efflux was under way caused a gradual sustained increase in efflux rate. It was concluded that uptake of 14C-salicylic acid by submaxillary glands in vitro occurs by passive diffusion of the un-ionized species across the cell membnane, followed by binding to an intracellular site. The binding site appears to be saturable and appears to favor the un-ionized species of the drug.
Footnotes
- Received October 22, 1970.
- Accepted January 4, 1971.
- © 1971, by The Williams & Wilkins Company
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