GROWTH OF MOUSE HEPATOCYTES IS STIMULATED BY GASTRIN

Hepatocyte growth is regulated by various growth factors, including epidermal growth factor (EGF) and insulin. Recently, several additional peptide hormones have been shown to stimulate growth of hepatocyte only in the presence of EGF or insulin and are thus termed secondary mitogens. Gastrin regulates growth of normal and neoplastic gastrointestinal tissues, but the effect on growth of hepatocyte is unknown. We examined the effect of gastrin on growth of a normal mouse hepatocyte (NMH) line established in our laboratory. Effect of gastrin-17 (G-17) (10(-8) to 10(-6) M) on growth of NMH cells was examined in either the presence or absence of EGF in the culture medium. Growth of NMH cells was evaluated by incorporation of either bromodeoxyuridine (BrdU) or H-3-thymidine and by counting cells. Presence of a cell surface receptor for G-17 was determined by Scatchard analysis using I-125-G-17. In the presence of EGF, gastrin stimulated growth of NMH cells; in the absence of EGF, gastrin did not affect growth. The stimulatory effect of gastrin on NMH cells was blocked by IMV 320, a CCK-B type receptor antagonist. NMH cells possess a single, high affinity binding site for gastrin (K-d = 1.2 nM); EGF increased the gastrin binding capacity compared to nontreated cells (3.5 +/- 0.4 vs. 2.2 +/- 0.6 fmol/10(6) cells). G-17 stimulated growth of NMH cells through a single high affinity receptor for G-17 which pharmcologically appears to be the CCK-B type only in the presence of EGF and thus can be considered a secondary mitogen. (C) 1995 Wiley-Liss, Inc.