The plasma membrane Fe(3+)-reductase activity of Caco-2 cells is modulated during differentiation.

The aim of the present study was to investigate whether the brush border membrane ferric reductase activity of Caco-2 cells is modulated during cell differentiation. The ferric reductase activity was determined in whole cells and isolated microvillous membranes at different stages of cell differentiation by measuring the amount of Fe3+ reduced during the incubation time. Our results indicated that the ferric reductase activity decreased in fastly growing cells and reactivated in postconfluent cells in contrast to the alkaline phosphatase and sucrase activities which were progressively expressed during differentiation as conventional indicators of cell maturity. The lowest ferric reductase activity was found in cells at the log phase of proliferation, while freshly seeded or highly differentiated cells had significantly higher enzyme activities. Cells grown under serum-free conditions had similar ferric iron reduction rates as cells propagated under standard conditions. Reagents or hormones affecting cell metabolism through different pathways had no significant effect on this transplasma membrane redox system.