EXPRESSION OF THE CALCIUM-SENSING RECEPTOR ON HUMAN ANTRAL GASTRIN CELLS IN CULTURE

The presence of the extracellular calcium-sensing receptor on human an tral gastrin cells was investigated, Reverse transcription PCR using m RNA isolated from gastrin cell-enriched cell cultures identified a pro duct with a sequence identical to part of the human parathyroid-secret ing cell calcium-sensing receptor. Immunocytochemistry with an antibod y to the extracellular region of the receptor immunostained all gastri n cells (but not mucin or somatostatin cells), and detected appropriat e-sized bands in Western blots of whole cell lysates. Increasing extra cellular calcium levels from 0.5 to 9 mM stimulated gastrin release in a concentration-dependent manner, with maximal release obtained at 7. 2 mM, A known agonist of the calcium receptor, spermine also stimulate d gastrin release, Microfluorimetry of identified gastrin cells demons trated that increasing extracellular calcium resulted in an initial ra pid rise in intracellular calcium followed by a plateau level that ret urned to basal levels immediately after removal of the elevated calciu m, The traces were consistent with activation of a receptor-mediated m echanism rather than a concentration-dependent influx of calcium, In c onclusion, these data indicate that G cells express the calcium-sensin g receptor, and that activation of the receptor may explain the acid r ebound phenomenon associated with calcium-containing antacid preparati ons.