Fig. 11. Anoga-DH₃₁ has natriuretic activity in tubules previously challenged with Musdo-K. Fluid secretion and urine Na⁺ and K⁺ concentrations were measured over 30 min intervals under control conditions and after the addition of 1 µmol l^–1 Musdo-K alone and then in combination with 1 µmol l^–1 Anoga-DH₃₁. Bars represent the means + S.E.M. for eight tubules. Fluid secretion (open bars) is stimulated 4-fold by Musdo-K, but the urine [Na⁺]:[K⁺] ratio (solid bars) is unchanged. Both parameters are increased >6-fold after the addition of Anoga-DH₃₁. Identical letters indicate values that do not differ significantly (P>0.05).