Fig. 6. The relationship between extracellular pHe (x) and relative Cl^- secretion rate (y) of the isolated-perfused rectal gland activated by 5x10^-6 mol l^-1 forskolin (closed symbols, data from Fig. 5 of the present study) and the rectal gland of intact, unanaesthetized dogfish activated by systemic volume loading [open symbols, data from Wood et al. (Wood et al., 2006)]. Data from every experimental treatment except acetazolamide are shown. Values are means ± 1 s.e.m. (N=5-7 for each treatment). The in vitro and in vivo data sets appear to follow a single relationship. The equation of the exponential regression line is: y=0.0441e^0.9784x (r=0.94, P<0.0001).