POLYAMINE METABOLISM OF ENTEROCYTE-LIKE CACO-2 CELLS AFTER EXPOSURE TO PHASEOLUS-VULGARIS LECTIN

The effect of Phaseolus vulgaris isolectin E(4) on polyamine concentra tions and ornithine decarboxylase activity of proliferating and differ entiating Caco-2 cells was investigated. Values of putrescine, spermid ine, and spermine in control cells were highest during the early phase of proliferative cell growth and lowest in the stationary phase. Phyt ohaemagglutinin E(4) significantly increased cellular polyamine values during the late proliferative phase of cell growth. Ornithine decarbo xylase activity was high during intensive proliferation and growth, bu t was lower when proliferation slowed down or ceased. Exposure of Caco -2 cells in the early proliferative phase of cell growth to increasing concentrations of the potent intestinal growth factor phytohaemagglut inin E(4) greatly stimulated enzyme activity. In contrast, the activit y of ornithine decarboxylase was not stimulated in Caco-2 cells of the late proliferative phase nor was there any increase in the enzyme act ivity in differentiating and fully differentiated cells of the station ary phase. Accordingly, when proliferating Caco-2 cells possessed the highest ornithine decarboxylase activity, the polyamine values were al so at their highest. During differentiation, as the ornithine decarbox ylase activity fell close to zero, polyamine values also decreased. In the early proliferative phase of cell growth ornithine decarboxylase activity coincided with DNA synthesis in cells exposed to Phaseolus vu lgaris isolectin E(4). These findings with Caco-2 cells were similar t o those found in brush border cells of the rat small intestine.