Figure 7. Effects of basolateral membrane permeablilization on dDAVP-stimulated I_sc.

I_sc was measured in sets of confluent cultures of +/+^(L), L/+ and L/L CCD cells grown on filters after the basolateral membrane had been permeabilized by adding nystatin (360 μg ml⁻¹) to the basal side of the filter, and a Cl⁻ gradient (basal medium: 149 mm; apical medium: 14.9 mm) imposed as described in the Methods. Nystatin (^) was added to the basal medium for 20 min. The cells were then sequentially incubated with basal dDAVP (10⁻⁸m, •) for 10 min, and then with apical NPPB (10⁻⁴m, δ) for a further 10 min. Similar I_sc recordings were performed on +/+^(L) CCD preincubated with 10⁻⁶m aldosterone for 4 h (+/+^(L)+Aldo) before permeabilization of the basolateral membrane (hatched bar). Bars represent the relative δI_sc increase caused by dDAVP. Values are means ± s.e.m. from five to seven separate experiments. *P < 0.05, **P < 0.01, ***P < 0.001versus untreated +/+^(L) values.