The presence of the extracellular calcium-sensing receptor on human antral gastrin cells was investigated. Reverse transcription PCR using mRNA isolated from gastrin cellenriched cell cultures identified a product with a sequence identical to part of the human parathyroid-secreting cell calcium-sensing receptor. Immunocytochemistry with an antibody to the extracellular region of the receptor immunostained all gastrin cells (but not mucin or somatostatin cells), and detected appropriate-sized bands in Western blots of whole cell lysates. Increasing extracellular calcium levels from 0.5 to 9 mM stimulated gastrin release in a concentrationdependent manner, with maximal release obtained at 7.2 mM. A known agonist of the calcium receptor, spermine also stimulated gastrin release. Microfluorimetry of identified gastrin cells demonstrated that increasing extracellular calcium resulted in an initial rapid rise in intracellular calcium followed by a plateau level that returned to basal levels immediately after removal of the elevated calcium. The traces were consistent with activation of a receptor-mediated mechanism rather than a concentration-dependent influx of calcium. In conclusion, these data indicate that G cells express the calcium-sensing receptor, and that activation of the receptor may explain the acid rebound phenomenon associated with calcium-containing antacid preparations.

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For an odd prime [Formula: see text], we determine a minimal set of topological generators of the pro-[Formula: see text] Iwahori subgroup of a split reductive group [Formula: see text] over [Formula: see text]. In the simple adjoint case and for any sufficiently large regular prime [Formula: see text], we also construct Galois extensions of [Formula: see text] with Galois group between the pro-[Formula: see text] and the standard Iwahori subgroups of [Formula: see text].