EFFECTS OF EXTRACELLULAR MG2-SECRETION IN RAT GASTRIC PARIETAL-CELLS(CONCENTRATION ON INTRACELLULAR SIGNALING AND ACID)

In the present study, the effects of extracellular magnesium concentra tion ([Mg2+](ex)) on stimulus-secretion coupling processes were invest igated in rat gastric parietal cells in vitro. Extracellular magnesium reduction resulted in (1) an increase of basal intracellular free cal cium concentration ([Ca2+](in)), (2) an enhancement of both carbachol and thapsigargin-induced calcium responses, (3) an improved filling st ate of intracellular calcium stores, (4) an increase of both basal and carbachol-induced acid secretion, whereas intracellular adenosine 3', 5'-cyclic monophosphate (cyclicAMP) levels and histamine stimulated ac id secretion were not affected. The effects of high [Mg2+](ex) were op posite to the described results, except that high [Mg2+](ex) was able to decrease significantly histamine-stimulated cyclicAMP levels and ac id secretion. These findings indicate a modulatory role of [Mg2+](ex) on the intracellular signalling processes and acid secretory propertie s in rat parietal cells. These effects seemed to be mediated by regula ting (1) calcium loading capacity of intracellular stores, (2) the per meability of the calcium influx pathway, and (3) the formation of cycl icAMP. (C) 1997 Elsevier Science B.V.