DIDS titration of sulfate transport. The influx of [35S]sulfate into the cells was measured at 10% hematocrit in isotonic citrate buffer (84 mM sodium citrate, 1 mM EGTA, 4 mM sodium sulfate [pH 6.5]). Influx was determined after 5 minutes at 30°C in the presence of different concentrations of DIDS. The lines show the results of linear regression analysis of the data. ● indicates control; ○, mother; and ▵, patient.