Mt. Nunez et al., ROLE OF REDOX SYSTEMS ON FE3-2) CELLS( UPTAKE BY TRANSFORMED HUMAN INTESTINAL EPITHELIAL (CACO), American journal of physiology. Cell physiology, 36(6), 1994, pp. 30001582-30001588
Caco-2 cells were used as a model of human intestinal epithelium to in
vestigate the role of redox systems in transepithelial transport of Fe
-59(3+). The cells reduced Fe3+ present in the apical medium; the redu
ction was 50% inhibited by adriamycin and p-chloromercuribenzoate. Add
ition of [C-14]ascorbate to the basolateral medium resulted in accumul
ation of C-14 radioactivity in both cells and apical medium; apical ra
dioactivity increased with time and was probably caused by paracellula
r flux. The cells provided Fe3+ reduction capacity to the apical incub
ation medium. Addition of ascorbate to the basolateral medium increase
d this reduction capacity a-fold and the cellular uptake of Fe-59(3+)
1.8-fold. Adriamycin significantly inhibited both cellular Fe-59 uptak
e and Fe transport into the basolateral side. The results indicate tha
t Caco-2 cells reduce apical Fe3+ by two parallel mechanisms: by a pla
sma membrane ferrireductase and by the secretion of reductants of eith
er cellular or basolateral origin. The data support a model for Fe3+ i
ntestinal absorption in which cell-mediated Fe3+ reduction occurs befo
re cellular Fe uptake.