AJP - Renal Physiology, Vol 250, Issue 2 226-F234, Copyright © 1986 by American Physiological Society
Sensitivity of rat renal luminal and contraluminal sulfate transport systems to DIDS
C. Bastlein and G. Burckhardt
4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) was tested as an
inhibitor of the sulfate transport systems in rat renal brush border and
basolateral membrane vesicles. Na+-driven sulfate uptake into brush border
membrane vesicles was half-maximally inhibited at 350 microM DIDS. Proton
gradient-driven sulfate uptake into basolateral membrane vesicles was
competitively inhibited by DIDS with a Ki of 2.4 microM. The Km for delta
pH-driven sulfate uptake was 5.4 microM. The different affinities of the
sulfate transport systems for DIDS correlated with different substrate
specificities. The luminal transport system accepted a smaller range of
anions than the contraluminal system and did not operate as a
Na+-independent anion exchanger. After treatment of basolateral membrane
vesicles with 50 microM DIDS at pH 8.4 for 30 min, an irreversible
inhibition of sulfate uptake was observed. With brush border membranes,
only a small irreversible inhibition was obtained. Lack of inhibition after
treatment of basolateral membranes with DIDS at pH 6.4 indicated that DIDS
reacted with deprotonated amino groups of the transport protein. Sulfate
was protected from the irreversible inhibition by DIDS. Sodium-driven
uptake of L-glutamate and methylsuccinate into basolateral membrane
vesicles was not irreversibly inhibited by DIDS, indicating a specific
action of DIDS on the contraluminal sulfate transport system. Irreversible
and substrate-protectable inhibition of sulfate transport render DIDS
suitable for future affinity labeling studies on the sulfate transport
system in basolateral membranes.
