Fig. 9. Effects of variation in saline ion composition on K⁺ flux. (A) Effects of changes in Na⁺ concentration and K⁺ concentration on K⁺ flux (mean ± S.E.M.). The key indicates saline K⁺ concentration in mmol l^–1. (B) Double-reciprocal plots of K⁺ flux vs bathing saline K⁺ concentration for salines containing the three Na⁺ concentrations (in mmol l^–1) indicated in the key. Data fit three straight lines described by the function y=0.62x+0.066 for tubules in 137.1 mmol l^–1 Na⁺, y=0.47x+0.071 for tubules bathed in 120 mmol l^–1 Na⁺ and y=0.395x+0.068 for tubules bathed in 98 mmol l^–1 Na⁺. N=8–10 tubules.