Phosphoinositides synthesis in desensitized rat pancreatic acinar
cells.
Lods, Jean-S[acute]ebastien, Bernard Rossignol, Catherine Dreux Et
Jean Morisset.
D[acute]epartement de biologie, Facult[acute]e des sciences,
Universit[acute]e de Sherbrooke, Sherbrooke, Qu[acute]ebec, Canada
J1K 2R1, Biochimie des Transports cellulaires
APStracts 2:0031G, 1995.
To help understand the possible role of phosphoinositide turnover in
the desensitization process, the availability of phosphatidylinositol
4,5-bisphosphate was investigated in normal and desensitized
pancreatic acinar cells treated with carbamylcholine (Cch), caerulein
(Cae) and the phorbol ester, 12-0-tetradecanoylphorbol-13-acetate
(TPA). In control acini, incorporation of myo-[3H] inositol into
total phosphoinositides (PI) was maximal at 120 min, Cch and Cae
dose-dependent, and insensitive to TPA. Cch stimulation increased the
proportion of myo-[3H] inositol incorporated into
phosphatidylinositol 4,5-bisphosphate (Ptd Ins (4,5)P2) whereas
caerulein specifically channeled myo[3H] inositol incorporation into
Ptd Ins (3,4) P2 and Ptd Ins (3,4,5) P3. In the desensitized cells,
preexposure to Cch and Cae but not to TPA increased the subsequent
basal rate of myo-[3H] inositol incorporation into total PI by 66%
and 50% above control values. There were no subsequent responses to
increasing concentrations of Cch, Cae and TPA during a second
incubation. Desensitization of the pancreatic secretory responses to
Cch, Cae and TPA does not seem to result from a decrease either in
total PI or in specific PTd Ins (4,5)P2 synthesis which is needed for
IP3 and diacylglycerol production.
Received 10 June 1994; accepted in final form 6 February 1995.
APS Manuscript Number G224-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 7 March 1995.