AJP - Gastrointestinal and Liver Physiology, Vol 258, Issue 6 974-G981, Copyright © 1990 by American Physiological Society
Synthesis and secretion of somatostatin-28 and -14 by fetal rat intestinal cells in culture
P. L. Brubaker, D. J. Drucker and G. R. Greenberg
Department of Physiology, University of Toronto, Ontario, Canada.
A fetal rat intestinal cell (FRIC) culture model was established to
investigate the factors controlling synthesis and secretion of
somatostatin-28 (S-28) by the intestine. Immunohistochemical analysis
demonstrated the presence of cells containing somatostatin-like
immunoreactivity (SLI), many of which emitted long processes toward
neighboring cells. Gel chromatography of SLI stored and secreted by
nonstimulated FRIC cultures demonstrated a predominance of S-28 (59%),
lesser amounts of S-14 (31%), and a minor peak of large molecular weight
SLI (10%). Secretion of SLI was stimulated by treatment of cells for 2 h
with 5 mM dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP; P less
than 0.01) or 2 microM phorbol ester (P less than 0.05), but was unaffected
by the calcium ionophore A23187 (2 micrograms/ml). Concomitant treatment
with all three agents increased SLI secretion in an additive fashion to 254
+/- 25% of controls (P less than 0.0001). DBcAMP treatment did not alter
the distribution of stored or secreted S-28 (59%) and S-14 (33%). After 24
h of exposure to DBcAMP, but not after treatment with phorbol ester, a
threefold increment in prosomatostatin mRNA transcript levels was observed.
FRIC cultures therefore synthesize and secrete a predominance of S-28 in a
regulated manner, making them a promising model for future studies on the
biosynthesis and secretion of intestinal somatostatin.
