Dietary intake is the sole source of Mg2? in human,
therefore adequate intestinal absorption of Mg2? is vital for
normal Mg2? balance. Intestinal Mg2? uptake comprises
saturable transcellular active and non-saturable paracellular
passive mechanisms [1–3], with the latter contributing
about 90 % of the total intestinal Mg2? absorption [3]. This
transport mechanism is driven by the electrochemical
gradient set up by a higher luminal Mg2? concentration and
lumen positive voltage with respect to the basolateral side
[1, 3, 4]. The tight junction-associated claudins (Cldn) have
been reported to act as a paracellular Mg2? channel within
the tight junction [5, 6]. However, the regulation of the
paracellular passive intestinal absorption of Mg2? is
unknown.