MITOGENIC PROPERTIES OF HUMAN GASTRIC-JUICE

This study was performed to define the biologically active growth modu lators in human gastric juice. Mitogenic activity was evaluated by the incorporation of [H-3]thymidine into 3T3 fibroblasts. A negative corr elation was observed between pH and mitogenic activity in gastric juic e (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 act ivity due to small molecule mitogens (less than 13 kDa), and growth in hibitory activity only in neutral samples due to a macromolecular subs tance (larger than 240 kDa) susceptible to trypsin digestion and heat and acid treatments. We conclude that acidity-dependent changes in mit ogenic activity observed in this study are due to appearance of acid-u nstable, high-molecular-weight, growth-inhibitory substance.