POLYAMINE DEFICIENCY IMPAIRS PROLIFERATION AND DIFFERENTIATION OF CULTURED ENTEROCYTES (CACO-2)

The polyamine dependence of enterocyte growth and differentiation was studied in the human intestinal cell line CaCo-2 using a specific inhibitor of the key enzyme ornithine decarboxylase (ODC), difluoromethylornithine (DFMO). ODC was highest during the initial phase of rapid growth and was inhibited in a dose dependent fashion by DFMO at 0.06-2 mM. At low levels DFMO only delayed cell replication without affecting final cell count whereas at concentrations of 0.125 mM and above the final cell number was diminished by at least 53% compared to controls. In contrast, DFMO even at 0.03 mM reduced sucrase activity to 44% of controls when added at day 2 but was ineffective when supplemented at day 7 of culture or later. The inhibitor also diminished the number and length of microvilli in a dose dependent fashion, although this effect required higher DFMO levels than the reduction of sucrase activity. The DFMO mediated suppression of cell replication, enzymatic and morphologic differentiation was reversible in the presence of the ODC product putrescine. Putrescine alone did not affect any of the above parameters. In conclusion, the present data suggest that ODC and polyamines are involved both in enterocyte growth and differentiation.