Fig. 3. Unidirectional secretory, unidirectional reabsorptive, and net PAH fluxes by chick PTCs following treatment with urate (330 µmol l^–1), urate and estrone sulfate in combination (ES + UA), or estrone sulfate (ES, 500 µmol l^–1) alone. All treatments were administered to the interstitial and luminal sides of the epithelium at t=–0.5 h. Data are presented as the percentage of the paired control secretory flux after 90 min exposure and are means ± S.E.M. of three preparations. ^*Significantly different from paired control flux (P<0.05, paired t-test).