Participation of polypeptide proteinase inhibitors in proliferation of fibroblasts.

The polypeptide proteinase inhibitors (PI) isolated from Cucurbitaceae plants, bovine pancreas, lima bean kale seeds and some other sources were assayed in mouse, rat and human cell cultures for possible mitogenic effects. PI stimulated the proliferation of the spare cultures of Balb/c 3T3 and NRK-49F fibroblasts pretreated with trypsin. PI had no effect on [3H]thymidine incorporation by the monolayer cultures of the mouse or rat cells. Also certain human cell lines were unresponsive to PI. The results suggest that PI have growth factor-like activities which are cell and/or species specific.