Effects of anion transport inhibitors and ion substitution on Cl- transport in TAL of Henle's loop

To identify the mechanism of Cl- transport across the thin ascending limb of Henle's loop (TAL), the authors examined effects of anion transport inhibitors and ionic substitution in the isolated segments of hamsters using the in vitro microperfusion technique. 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) at 10-3 M changed the NaCl diffusion voltage (Vt) to the orientation that corresponds to the decrease in the Cl--Na+ permeability ratio when it was added either to the bath or to the lumen. DIDS, added to the bath or to the lumen decreased the lumen-to-bath flux coefficient for 36Cl, whereas it had little effect on the flux coefficient for 22Na. The inhibitory effect of phloretin was rapid and reversible. Phloridzin was ineffective. From these observations, they conclude that Cl- transport across the TAL is distinct from Na+ and is not coupled with Na+, K+, or HCO-3