Fig. 8. Concentration–response curves for secreted fluid TEA concentration as a function of bathing saline TEA concentration for the main segment (A) and whole tubule (B). Concentration–response curves for TEA flux as a function of bathing saline TEA concentration for the main segment (C) and whole tubule (D). Each point shows the mean ± S.E.M. for N=6–16 main segments or 3–8 whole tubules. The insets in the upper panels reflect the corresponding arrangements of the tubules and bathing droplets. A droplet of secreted fluid (SF) is indicated by the open circle. Abbreviations U, ureter; D, distal segment; M, main segment; L, lower segment.