GROWTH-REGULATION OF RABBIT GASTRIC EPITHELIAL-CELLS AND PROTOONCOGENE EXPRESSION

We recently developed a primary culture system for gastric epithelial cells from adult rabbits that allows the investigation of growth regul ation at the cellular level. In this study, we demonstrated that epide rmal growth factor (EGF), insulin, and dibutyryl adenosine 3',5'-cycli c monophosphate (dBcAMP) all stimulated cell proliferation. Insulin an d dBcAMP potentiated the stimulation of cell proliferation by EGF, whi le transforming growth factor-beta 1 (TGF-beta 1) inhibited it. Expres sion of c-fos and c-myc was induced in response to the stimulation by these growth regulators, but the degree of expression did not necessar ily correlate with the effects of these agents on cell proliferation. In conclusion, EGF, insulin, and dBcAMP were positive growth regulator s, while TGF-beta 1 was a negative regulator in gastric epithelial cel ls. These growth modulators may exert their effects by distinct pathwa ys from a standpoint of the expression of c-fos and c-myc.