Figure 9.

The rheogenic nature of GABA transport in short-circuited Caco-2 cell monolayers. Epithelial monolayers of Caco-2 cells were continually short-circuited in Na⁺-free media and the short-circuit current (I_SC) response measured. (a) Time dependence of inward I_SC after incubation in apical media of pH 5.5 (basolateral pH 7.4) and exposure to 20 mM GABA (see arrow). Square-wave pulse is excursion of the voltage-clamp to +1 mV as a measure of epithelial conductance. Representative trace of ten individual experiments. (b) Maximal ΔI_SC in the presence of GABA and GABA analogues (all 20 mM) in Na⁺-free media at apical pH 5.5 (basolateral pH 7.4). Results are expressed as a percentage of the response to GABA (mean±s.e.mean, n=6–10; ^*, P<0.05 versus GABA; ^**, P<0.01 versus GABA).