AJP - Endocrinology and Metabolism, Vol 246, Issue 4 361-E368, Copyright © 1984 by American Physiological Society
A dual role of calcium in release of somatostatin from canine gastric antral mucosa
G. Pittenger, A. I. Vinik, R. G. Fiddian-Green and L. Wagner
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.
