The plasma membrane Fe3+-reductase activity of Caco-2 cells is modulated during differentiation

The aim of the present study was to investigate whether the brush border me mbrane ferric reductase activity of Caco-2 cells is modulated during cell d ifferentiation. The ferric reductase activity was determined in whole cells and isolated microvillous membranes at different stages of cell differenti ation by measuring the amount of Fe3+ reduced during the incubation time. O ur results indicated that the ferric reductase activity decreased in fastly growing cells and reactivated in postconfluent cells in contrast to the al kaline phosphatase and sucrase activities which were progressively expresse d during differentiation as conventional indicators of cell maturity. The l owest ferric reductase activity was found in cells at the log phase of prol iferation, while freshly seeded or highly differentiated cells had signific antly higher enzyme activities. Cells grown under serum-free conditions had similar ferric iron reduction rates as cells propagated under standard con ditions. Reagents or hormones affecting cell metabolism through different p athways had no significant effect on this transplasma membrane redox system .