GASTRIN EFFECTS ON ISOLATED RAT ENTEROCHROMAFFIN-LIKE CELLS IN PRIMARY CULTURE

The hormone gastrin stimulates acid secretion by releasing histamine f rom gastric enterochromaffin-like (ECL) cells and induces ECL cell pro liferation in vivo. This study uses a > 90% pure ECL cell preparation in culture to compare gastrin effects on histamine release, histidine decarboxylase (HDC) activity, and DNA synthesis. Gastrin and the chole cystokinin octapeptide (CCK-8, nonsulfated) induced histamine release from ECL cells (24-96 h of primary culture) within 5 min of incubation [concentration eliciting 50% of maximal response (EC(50)), 4 and 2 x 10-(11) M, respectively]. The CCK-B antagonist L-365,260 inhibited thi s effect [concentration inhibiting 50% of maximal response (IC50), 2 x 10(-8) M], whereas the CCK-A antagonist L-364,718 (10(-8) M) and the tyrosine kinase inhibitor genistein (10(-4) M) had no effect. Histamin e release was associated with a biphasic elevation of intracellular Ca 2+. Gastrin stimulated HDC activity two- to threefold after 60 min of incubation (EC(50), 10(-10) M). Gastrin also increased DNA synthesis i n ECL cells, with an EC(50) of 1.7 x 10(-12) M as measured by the inco rporation of 5-bromo-2'deoxyuridine (BrdU). Positive nuclear immunosta ining increased two- to threefold in up to 20% of ECL cells after 48-9 6 h of incubation. This effect was inhibited by L-365,260 (IC50, 5 x 1 0(-9) M) and by genistein (10(-4) M) but was not altered by L-364,718 (10(-8) M). The antisecretory drugs omeprazole, lansoprazole, and pant oprazole did not affect BrdU incorporation in isolated ECL cells. In c onclusion, acute and chronic gastrin effects on the ECL cell are media ted via CCK-B receptors but differ in apparent receptor affinity and s ignal transduction pathways.