A dual role of calcium in release of somatostatin from canine gastric antral mucosa.
We have examined the factors regulating the mucosal release of somatostatin-like immuno-reactivity (SRIF-LI) from 1-cm2 sheets of isolated canine gastric antral mucosa mounted in a Ussing chamber. SRIF-LI was released predominantly into the luminal perfusate, was maximal at pH 2.5, 1,987 +/- 319 pg X ml-1 X h-1, and reached a nadir at pH 6.0 of 89 +/- 24 pg X ml-1 X h-1. Increasing extracellular Ca2+ to 10 mM stimulated the release of SRIF-LI at both high and low pH. The Ca2+ ionophore A23187 had no apparent effect at either pH 2.5 or 7.0. LaCl3 stimulated the release of SRIF-LI at pH 7.0 but not at pH 2.5. Ouabain and TMB-8 had no significant effect on the release of SRIF-LI. At pH 7.0, trifluoperazine (TFP) stimulated release of SRIF-LI (80 +/- 10 pg X ml-1 X h-1). EGTA stimulated release of SRIF-LI at pH 2.5 (1,134 +/- 137 pg X ml-1 X h-1) and at pH 7.0 (300 +/- 57 pg X ml-1 X h-1), which was reversed by replacement of Ca2+ (22 +/- 6 pg X ml-1 X h-1). Thus Ca2+ appears to exert a dual effect on the release of SRIF-LI: both an increase and depletion of extracellular Ca2+ release SRIF-LI.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002712:Chlorides / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D004285:Dogs; D005753:Gastric Mucosa / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009994:Osmolar Concentration; D012636:Secretory Rate / Q000187:drug effects; D013004:Somatostatin / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology
D002712:Chlorides; D014268:Trifluoperazine; D013004:Somatostatin; D000242:Cyclic AMP; D002118:Calcium