Characterization of the release of cholecystokinin and secretin from a murine intestinal tumor cell line

122 CHARACTERIZATION OF THE RELEASE OF CHOLECYSTOKININ AND SECRETIN FROM A MURINE INTESTINAL TUMOR CELL LINE. Chang CL, Chang TM, Leiter A*, and Chey WY. The Genesee Hospital and University of Rochester Medical Center, Rochester, NY 14607, *Tufts University, Boston, MA, U.S.A. The release of cholecystokinin (CCK) and secretin was studied in a murine intestinal endocrine tumor cell line, STC-1 (Am J Pathol, 136, 1349, 1990). The cells in monolayer cultures at 80% confluency contained 227.6 ± 17.5 fmol/mg and 50.7 _+ 6.5 fmol/mg cell protein of CCK-LI and S-LI, respectively. The cells were incubated in Hepes-buffered Earle's balance salt solution containing protease inhibitor and bovine serum albumin in the absence or presence of various stimulating agents at 37 ° C or 4 ° C for 2 h or various periods of time under 95% 02/5% CO2. The amount of CCK-LI or S-LI released into the medium and retained in the cells was determined by the corresponding specific radioimmunoassays. The release of both CCK-LI and S-LI was stimulated by 0.1 /aM g-12-tetradecanoylphorbol-13-acetate (826% vs control in CCK-LI, 216% in S-LI, respectively), 30 pM forskolin (231%, 157%), 1 pM A23187 (112%, 35%), 2 mM dibutyryl cAMP (58%, 31%). The effects of these stimulants were also time- and dose-dependent. The release of CCK-LI and S-LI was also stimulated by various luminal stimulants including Na oleate, camostate and an anti-ulcer agent, plaunotol. Isobutylmethyl xanthine (0.5 mM) potentiated the effect of dibutyryl cAMP, forskolin and plaunotol. The release of CCK-LI was also significantly stimulated by L-tryptophan (20 mM) and bombesin (10 .8 M). Analysis by HPLC of the medium indicated that CCK-LI and S-LI with retention times the same as those of CCK-8 and rat intestinal S-LI, respectively were released. These results, like those observed in CCK and secretin cells-enriched mucosal cells isolated from rat duodenum, indicated involvement of cAMP, Ca 2 and protein kinase C in the release of these hormones. Thus, STC-1 cells which are more homogenous and provided more sensitive and consistent responses than the mucosal cells should serve as a good model for studying the release mechanisms of CCK and secretin.

EFFECTS OF PORTACAVA SHUNT ON ULTRASTRUCTURE OF ECL CELLS IN THE STOMACH OF RATS WITH OMEPRAZOLE-EVOKED HYPERGASTRINEMIA Chen D: Hltkanson R and Sundler F, Depts of Pharmacology and Medical Cell Research, University of Lund, Lund, Sweden The ECL cells are the predominent endocrine cell type in the acid-producing part of the rat stomach. The hyperplastic response of the ECL cells to omeprazole-evoked liy~.rgastrinemia is exaggerated tiy portacava slaunt (PCS) (1). The present report describes how the ECL cells respond ultrastructually to PCS or omeprazole treatment al.one or a combination of PCS and omeprazole treatment. Sprague-Dawley rats were subjected to PCS,or omeprazole treatment (400-u.mol/kg/day, orally}, or the combination of PCS and omeprazole treatment. Control rats were sham-operated. The rats were killed 8-10 weeks after starting omeprazole treatment. The results confirm earlier observations that PCS or omeprazole treatment alone induces changes in the ECL cells, manifested in an increased number and size and in enlarged cytoplasmic vesicles (2,3) and showed that the combination of PCS and omeprazole treatment produced a greatly enhanced ECL cell hypertrophy and a significant reduction in the number of secretory. granules/vesicles per unit cytoplasm. Another prominent feature was the predominance of large, vacuolated cytoplasmic vesicles in the ECL cells of PCS rats and of omeprazole-treated rats. This was partacuIarly apparent in the ECL cells of the omeprazole-treated "I~CS rats. The proportion of granules versus vesicles was much lower in ECL cells from rats subjected to the combination of PCS and omep.razole treatment than in ECL cells from control rats. In conclusion, the combination of PCS and long-lasting hypergastrinemia (omeprazole treatment daily for 8-10 weeks) produced a greatly en-hanced-ECL cell hypertrophy, a reduction in the number of secretory granules/vesicles per unit cytoplasm, and large vacuolated cytoplasmic vesicles in the ECL ceils. Ref. (1) Axelson J e t al, Gastroenterology, 1990,99,638-640 (2) H/tkanson R et al, J Physiol, 1976, 259,785-800; (3) BStteher C et al, Cell Tissue Res, 1989,256:247-257