The
AC sends cytoplasmic processes into the larger CC,
which emerge at the apical surface to form a
complex mosaic. Notably, the tight junctions found
between CC and AC contain fewer strands than do
those formed with PVCs (Sardet et al., ’79;
Kawakara et al., ’82). Therefore the AC interdigitations
within the CC apical membrane would
greatly increase the linear distance of leaky tight
junction, which is functionally important for the
paracellular sodium efflux (see Marshall, 2002,
this issue). There is also ample evidence that Cl
efflux occurs transcellularly through the CC
(Marshall, 2002, this issue).