GROWTH OF MOUSE HEPATOCYTES IS STIMULATED BY GASTRIN

Hepatocyte growth is regulated by various growth factors, including ep idermal growth factor (EGF) and insulin. Recently, several additional peptide hormones have been shown to stimulate growth of hepatocyte onl y in the presence of EGF or insulin and are thus termed secondary mito gens. Gastrin regulates growth of normal and neoplastic gastrointestin al tissues, but the effect on growth of hepatocyte is unknown. We exam ined 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 pre sence 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 f or 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 absenc e of EGF, gastrin did not affect growth. The stimulatory effect of gas trin on NMH cells was blocked by IMV 320, a CCK-B type receptor antago nist. NMH cells possess a single, high affinity binding site for gastr in (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 rece ptor 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.