Fig. 3. Effect of bath and luminal [K⁺] steps on V_bl. (A) Voltage trace from a collecting duct cell. The effect of changing bath [K⁺] from 3 to 20 mmol l^-1. (B) Summary data illustrating the effect of increasing bath [K⁺] from 3 to 20 mmol l^-1 on V_bl from collecting duct cells. (C) Summary data illustrating the effect of the bath [K⁺] step on V_bl from collecting tubule cells. (D) Voltage trace from a collecting duct cell. Effect of the luminal [K⁺] step. (E) Summary data illustrating the effect of increasing luminal [K⁺] from 3 to 20 mmol l^-1 on V_bl from collecting duct cells. (F) Summary data illustrating the effect of the luminal [K⁺] step on V_bl from collecting tubule cells. C, control solution; K_20,b, high [K⁺] in bath; K_20,l, high [K⁺] in lumen.