Calbindin-D28k is a member of the calcium-binding protein superfamily that includes calmodulin and troponin C. It is a cytosolic calcium binding protein highly expressed in the distal tubule,intestines,central nervous system,primary murine osteoblast cells and in several other organs. It plays an important role in the intracellular calcium homeostasis,its strong buffering capacity prevents cytotoxic effect of high concentration of free calcium in kidney,brain,pancreas,and intestine.