Fig. 6. Effect of 10^–4 mol l^–1 hydrochlorothiazide on secretion rate (mean ± S.E.M.) of tubules bathed in control saline and K⁺-free saline. Tubules were exposed to the vehicle alone (filled symbols; 0.1% ethanol) or to the vehicle plus hydrochlorothiazide (open symbols). Arrows indicate the time of addition of hydrochlorothiazide. The number of tubules per group is indicated in parentheses.