Fig. 6. Representative recordings of the K⁺ concentration (blue line) of urine secreted by tubules challenged with either (A) 1 µmol l^–1 Anoga-DH₄₄ or (B) 1 µmol l^–1 Anoga-DH₃₁. The concentration of Na⁺ (red line) in the secreted fluid was calculated assuming the sum of Na⁺ and K⁺ concentrations was 200 mmol l^–1. Arrows show the time of addition of the diuretic peptides.