Extracellular CaSR were expressed along the
entire length of the gastrointestinal tract (Geibel and
Hebert, 2009) and also in Caco-2 monolayers
(Davies et al., 2008). CaSR played a role in gastric
acid secretion, intestinal fluid absorption and
secretion, and colonic fluid secretion (Geibel and
Hebert, 2009). In the renal epithelium, CaSR
activation suppressed the paracellular passive Mg2+
transport by controlling Cldn-16 function in the tight
junction (Ikari et al., 2008). In the present study,
CaSR agonists neomycin and apermine were found
to have no effect on passive Mg2+ transport in both
control and omeprazole treated monolayers (Figure
4C). Our results agreed with a previous study that
showed regulation of paracellular passive Ca2+
transport across Caco-2 monolayers by extracellular
Ca2+ in a CaSR-independent mechanism (Davies et
al., 2008). Therefore, omeprazole was likely to
inhibit the intestinal passive Mg2+ absorption in a
CaSR-independent manner