The Ca2-mobilizing effects of gastrin and CCK-8 were prevented by proglumide, benzotnlpt, and the specific gastrln/CCKB receptor antagonist L365260. Gastrin stimulated the clonal growth of H510 cells

Gastnin has been postulated to be a physiological growth factor, but compelling in vitro evidence of this has been difficult to obtain. In the present study we investigated whether small cell lung carcinoma cell lines could provide a useful model system to study the effects of gastrin on signal transduction and cell proliferation in vitro. We found that the addition of gastrin to small cell lung cancer cells loaded with the fluo rescent Ca2 indicator fura 2-tetraacetoxymethylester causes a rapid and transient increase In the intracellular concentration of Ca2@ (lCa2i@)followedby homologousdesensitization. The tCa2@I1 response was especially prominent in the small cell lung carcinoma cell line H51O. In this cell line, gastnin I, gastrin H, cholecystokinin residues 26-33 (CCK-8), and unsulfated CCK-8 increased lCa2i1 in a concen tratlon-dependent fashion with half-maximum effects at 7, 23, 3, and 5 flM, respectively. The Ca2-mobilizing effects of gastrin and CCK-8 were prevented by proglumide, benzotnlpt, and the specific gastrln/CCKB receptor antagonist L365260. Gastrin stimulated the clonal growth of H510 cells in semisolid (agarose-containing) medium, increasing both the number and the size of the colonies. Gastrin and CCX agonists were equally effectivein promoting clonal growth. The broad-spectrum neuropeptide antagonists It-Arg',n-Phe@-Trp7'9,Leu―l substance P and IArg6,nTrp7'9,MePhe@@substance P (6-11) markedly inhibited gastnin-stimu lated Ca2 mobilization and clonal growth. These results show that gastnin acts as a direct growth factor through gastnin/CCKB receptors and demonstrate, for the first time, that these peptides can stimulate the proliferation of ceUsoutside the gastrointestinal tract.