AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 3 247-G254, Copyright © 1980 by American Physiological Society
Phosphatidylinositol turnover and calcium movement in the rat pancreas
P. Calderon, J. Furnelle and J. Christophe
Carbamylcholine, bombesin, pancreozymin, and pentagastrin elicited a
similar increase in amylase secretion and phosphatidylinositol turnover in
rat pancreatic fragments. The concentration of each secretagogue that
provoked half-maximal stimulation of amylase secretion was three to six
times lower than that which induced half-maximal stimulation of
phosphatidylinositol turnover. The increased turnover of
phosphatidylinositols due to carbamylcholine or pancreozymin, but not the
secretory response, persisted in a calcium-free medium or in 90% heavy
water. The replacement of the media Na+ with Li+ increased an
atropine-resistant turnover of phosphatidylinositols, but did not stimulate
secretion. The ionophore A-23187 (in a medium containing 2.5 mM Ca2+) and
10 mM NaF induced a high secretory response, but exerted no effect on
phosphatidylinositol turnover. K+ at a 70 mM concentration provoked a
phosphatidylinositol effect and hypersecretion. Secretin, vasoactive
intestinal peptide, dibutyryl cAMP, dibutyryl cGMP, 8-bromo cGMP, and
N2-monobutyryl cGMP stimulated amylase secretion without an increased
turnover of phosphatidylinositols. It is concluded that, in the rat
pancreas, the increased turnover of phosphatidylinositols was directly
associated with secretagogues inducing calcium movements.
