Fig. 5. Effects of 10^-5moll^-1 bumetanide on (A) fluid secretion rate, (B) K⁺ flux and (C) Na⁺ flux in serotonin-stimulated tubules. At t=10 min, bumetanide was added to the Malpighian tubules in the experimental group (open circles) and vehicle (0.1% ethanol) was added to the control group (filled circles). Data are expressed as means ± S.E.M. Asterisks indicate significant differences (P<0.05) between the control and experimental groups; N=7 for the experimental group and N=10-12 for the controls.