AJP - Renal Physiology, Vol 250, Issue 4 627-F632, Copyright © 1986 by American Physiological Society
Ascorbic acid transport in mammalian kidney
R. C. Rose
Ascorbic acid is known to circulate free in the plasma of several species
and is therefore filtered in the kidney; reabsorption subsequently takes
place and prevents urinary loss. However, no specific mechanism of renal
ascorbic acid transport has previously been presented. In the present
study, rat and guinea pig kidney were incubated as slices or as isolated
tubules in vitro in the presence of low concentrations of [14C]ascorbic
acid. The kidneys of both species handle ascorbic acid similarly. Ascorbic
acid accumulates in the renal tissue to a concentration three to four times
that present in the bathing media. Recently absorbed ascorbic acid diffuses
freely from the kidney and is predominantly nonmetabolized during
absorption. Uptake is reduced following replacement of bathing solution
sodium by lithium or cesium, or when incubation is performed in the
presence of metabolic inhibitors or at low temperatures. The results
indicate that ascorbic acid is reabsorbed in the kidney by a
sodium-dependent active transport mechanism that operates by concentrating
ascorbic acid in the cellular fluid. Renal slices and tubules both appear
to transport ascorbic acid and galactose across the brush-border membrane;
this indicates that the tubular lumens in these preparations are not
collapsed or sealed off.
