Expression of an extracellular calcium-sensing receptor in rat stomach

Background & Aims: Circulating levels of Ca2+ can influence secretory funct ions and myoelectrical properties of the stomach. A Ca2+-sensing receptor ( CaR) has recently been identified in tissues that regulate systemic Ca2+ ho meostasis, The aim of this study was to evaluate expression of CaR in the s tomach of the rat. Methods: In forestomach and glandular stomach, reverse-t ranscription polymerase chain reaction was used to amplify a 380-base pair product, which is 99% homologous with transcripts obtained in parathyroid a nd kidney. Results: Northern analysis of gastric mucosal polyA(+) RNA revea led 7.5- and 4.1-kilobase transcripts, similar to those obtained in rat par athyroid and kidney. Immunohistochemistry revealed CaR expression in region s of the submucosal plexus and myenteric neurons. In sections of intact tis sue, preparations of primary culture surface cells and surgically dissected gastric glands, staining was observed consistently in epithelial cells of the gastric glands and in gastric surface cells. In parietal cells in isola ted gastric glands, intracellular levels of Ca2+ responded to conditions th at are known to activate CaR, Conclusions: These are the first reported obs ervations that CaR is expressed in different epithelial cells of mammalian gastric mucosa and its enteric nerve regions, The effects of extracellular Ca2+ on gastric function may be attributable to activation of CaR.