Fig. 4. Anoga-DH₃₁ stimulates diuresis and natriuresis, mimicking the actions of exogenous cAMP. Fluid secretion and urine Na⁺ and K⁺ concentrations were initially measured over a 30 min control period and then at 10–15 min intervals after the addition of 1 µmol l^–1 Anoga-DH₃₁ alone (first arrow) and then in combination with 1 mmol l^–1 8-bromo-cyclic AMP (second arrow). Data points show the means ± S.E.M. for five tubules. (A) Anoga-DH₃₁ stimulates fluid secretion (solid line) and increases the urine [Na⁺]:[K⁺] ratio (broken line) to the same extent as 8-bromo-cyclic AMP. (B) Transepithelial Na⁺ transport (solid line) is selectively stimulated by Anoga-DH₃₁, which has relatively little effect on K⁺ transport (broken line).