Mitogenic properties of human gastric juice

This study was performed to define the biologically active growth modulators in human gastric juice. Mitogenic activity was evaluated by the incorporation of [3H]thymidine into 3T3 fibroblasts. A negative correlation was observed between pH and mitogenic activity in gastric juice (r = -0.45, P < 0.01). The concentrations of epidermal growth factor (EGF), transforming growth factor-alpha and -beta 1 (TGF-alpha and -beta 1), platelet-derived growth factor (PDGF), and basic fibroblast growth factor (bFGF) in gastric juice did not explain these changes in mitogenic activity. Gel filtration identified growth-stimulating activity due to small molecule mitogens (less than 13 kDa), and growth inhibitory activity only in neutral samples due to a macromolecular substance (larger than 240 kDa) susceptible to trypsin digestion and heat and acid treatments. We conclude that acidity-dependent changes in mitogenic activity observed in this study are due to appearance of acid-unstable, high-molecular-weight, growth-inhibitory substance.