Fig. 4.

Effect of iberiotoxin (IbTX) on FSK-induced I_sc and active K⁺ secretion in rat distal colon. A: time course of I_sc in the absence and in the presence of FSK and VO₄. VO₄ (1 mM) was added to mucosal bath, whereas 10 μM FSK was added to serosal bath (FSK/VO₄). I_sc in the presence of FSK/VO₄ was also measured in additional presence of 100 nM mucosal [IbTX (m)] and serosal [IbTX (m/s)] IbTX. B: m-s, s-m, and net K⁺ fluxes were measured in the presence of FSK/VO₄ (white bars). The K⁺ fluxes were also measured in the presence of mucosal [IbTX (m); gray bars] and serosal [IbTX (m/s); black bars] IbTX. Both I_sc and K⁺ fluxes were measured under voltage-clamp conditions. *P < 0.001, compared with respective fluxes in the absence of IbTX.