Transferrin stimulates iron absorption, exocytosis, and secretion in cultured intestinal cells
Nuñez, M.T.; Tapia, V.
American Journal of Physiology 276(5): C1085-C1090
1999
ISSN/ISBN: 0002-9513 PMID: 10329956 Document Number: 507999
The cellular mechanism by /Nhich basolateral transferrin (Tf) produces an increase in apical-to-basolateral Fe flux in Caco-2 cells was analyzed. After a pulse of 59Fe from the apical medium, three types of basolateral 59Fe efflux were found: a 59Fe efflux that was independent of the presence of Tf in the basolateral medium, a 59Fe efflux in which 59Fe left the cell bound to Tf, and a Tf-dependent 59Fe efflux in which 59Fe came off the cell not bound to Tf. Furthermore, addition of Tf to the basolateral medium doubled the exocytosis rate of Tf and increased the secretion of apolipoprotein A, a basolateral secretion marker. Both apotransferrin and Fe-containing Tf produced similar increases in 59Fe efflux, Tf exocytosis, and apolipoprotein A secretion. The Ca2+ channel inhibitor SKF-96365 inhibited both the Tf-mediated increase in transepithelial Fe transport and the secretion of apolipoprotein A. Thus the activation of transepithelial Fe transport by Tf seems to be mediated by Ca2+ entry into the cells. Reprinted by permission of the publisher.