Fig. 5. Dose–response curves showing % inhibition of fluid secretion rate (mean ± S.E.M., N=6–14) versus bumetanide concentration for tubules bathed in control saline () and K⁺-free saline (). Percentage inhibition was calculated as 1–(secretion rate of bumetanide-treated tubule/mean secretion rate of control tubules)x100. Data were calculated using the t=55 min values in Fig. 4 and were fit to the Michaelis–Menten equation using non-linear regression analysis, giving r² values for the control and K⁺-free data of 0.94 and 0.98, respectively.