Comments on the essentiality of calbindin-D9k and calcium channel TRPV6 for optimal active intestinal calcium transport in vitro

摘要

Calbindin-D9k, a vitamin D-induced calciumbinding protein discovered in rat intestine over 40 years ago,~1 has a molecular weight of about 9000 Da and binds two calcium ions per molecule with high affinity.~2 A current hypothesis sug-gests that calbindin-D9k might function as part of the energy-dependent intestinal calcium absorp-tion process, possibly serving as an intracellular cal-cium ferry, accelerating the flow of calcium from the microvillar pole of the enterocyte to the basallateral membrane.' Entrance of luminal calcium into the enterocyte is via the calcium entrance channel TRPV6,6'7 and exit into the lamina propria is by way of an ATP-dependent calcium pump. The microvillar calcium channel TRPV6, calbinain-D9k, and the calcium pump associated with the basallateral membrane all have vitamin D dependency.