Contraluminal sulfate transport in the proximal tubule of the rat kidney. III. Specificity: disulfonates, di- and tri-carboxylates and sulfocarboxylates.

In order to study the specificity for the contraluminal sulfate transport system the inhibitory potency of disulfonates, di-, tricarboxylates and sulfocarboxylates on the 35SO4(2-) influx from the interstitium into cortical tubular cells in situ has been determined. The following was found: Methane- and ethane-disulfonate as well as benzene-1,3-disulfonate inhibit contraluminal 35SO4(2-) influx (with an (app. Ki of less than 6 mmol/l), while benzene-1,2- and 1,4-disulfonate do not. The inhibitory potency of 1,3-benzene disulfonate is slightly augmented by an additional NH2- or OH-group in position 4. However, OH-groups at position 4 and 5 or 4 and 6 abolish the inhibitory potency. The naphthalene disulfonates tested inhibit only if they have an OH-group in ortho-position to one SO3H group. The stilbene disulfonates H2DIDS and DNDS inhibit the contraluminal 35SO4(2-) influx with high (app. Ki approximately equal to 0.8 mmol/l), DADS with lower potency (app. Ki approximately equal to 6 mmol/l). Amongst the tested aliphatic di- and tricarboxylates inhibition was exerted by oxalate (app. Ki 1.1 mmol/l) and maleate (app. Ki 3.8 mmol/l), but not by malonate, hydroxymalonate and citrate. Out of the tested benzene-dicarboxylates only those inhibit which have the COO- -groups directly on the ring in 1,2 and 1,3 position (app. Ki 4.0 and 2.7 mmol/l), but not in the 1,4 position. An additional OH-group in position 4 augments the inhibitory potency of 1,3 benzene-dicarboxylates (app. Ki 0.8 mmol/l), while an OH group on position 5 abolishes it.(ABSTRACT TRUNCATED AT 250 WORDS)