INSULIN ENHANCES EPIDERMAL GROWTH FACTOR-ALPHA-STIMULATED AND TRANSFORMING GROWTH FACTOR-ALPHA-STIMULATED GROWTH IN PRIMARY CULTURES OF GUINEA-PIG GASTRIC MUCOUS EPITHELIAL-CELLS

The effect of insulin on epidermal growth factor (EGF)- and transforming growth factor-alpha (TGF-alpha)-induced cell proliferation was examined in primary cultures of gastric surface mucous epithelial cells by using changes in cell counts and DNA as indices of cell growth. With 1.0% fetal bovine serum and Dulbecco's modified Eagle medium (low-serum DMEM) there was no effect of bovine insulin (0.1-10.0-mu-g/ml) on cell growth. Higher doses of insulin (20.0-mu-g/ml) in low-serum DMEM were able to stimulate growth of these cells compared with controls. In low-serum DMEM with no insulin the lowest effective dose of EGF or TGF-alpha for stimulating cell growth was 10 nM and 5 nM, respectively. In low-serum DMEM containing 2.5-mu-g/ml insulin there was a dose-dependent increase in cell growth with EGF and TFG-alpha at concentrations of 0.5-10.0 nM. The addition of insulin alone at 2.5-mu-g/ml, EGF alone at 2 nM, or TGF-alpha alone at 2 nM in serum-free DMEM media had no effect on gastric surface mucous cell DNA. In serum-free DMEM media with 2.5-mu-g/ml insulin, the addition of 2 nM EGF or 2 nM TGF-alpha caused an increase in both cell counts and DNA of 1.80- and 3.50-fold, respectively. The present study demonstrates that insulin, at concentrations that are not mitogenic, will enhance the proliferative effects of EGF and TGF-alpha on the growth of primary cultures of guinea pig gastric surface mucous epithelial cells.