CA2-SENSING RECEPTORS IN INTESTINAL EPITHELIUM()

Expression of Ca2+-sensing receptors (CaR) was demonstrated in several human intestinal epithelial cell lines (T84, HT-29, and Caco-2) and i n rat intestinal epithelium by both reverse transcriptase-polymerase c hain reaction (PCR) and Northern blotting of RNA. Restriction patterns of the PCR products were of the sizes predicted by the human and rat sequences. CaR agonists (Ca2+, poly-L-arginine, prot amine) mediated a n increase in intracellular Ca2+ in HT-29-18-C1 cells (monitored by ch anges in fura 2 fluorescence), which was dependent on release from tha psigargin-sensitive stores. U-73122, an inhibitor of phosphatidylinosi tol-phospholipase C, eliminated the CaR agonist-mediated rise in intra cellular Ca2+, whereas its inactive analog, U-73343, had no effect. Pe rtussis toxin pretreatment had no effect on CaR agonist-mediated modul ation of intracellular Ca2+. Taken together, these studies demonstrate that CaR are expressed in intestinal epithelial cells and couple to m obilization of intracellular Ca2+. The presence of CaR in intestinal e pithelial cells presents a new locus for investigations into the role( s) of extracellular Ca2+ in modulating intestinal epithelial cell diff erentiation and transepithelial Ca2+ transport.