A search for a mucosal iron carrier. Identification of mucosal fractions with rapid turnover of Fe⁵⁹

Iron absorption by the intestinal mucosa, which is increased following phlebotomy, may be mediated by a carrier. A carrier for iron should show prompt uptake of iron introduced into the intestinal lumen and rapid transfer of the iron into the carcass. When iron absorption is increased movement of iron across the mucosa by this postulated carrier should take place at an accelerated rate. In an effort to identify mucosal fractions with these properties, the distribution of Fe⁵⁹ between various fractions of guinea pig intestinal mucosa immediately after an intraluminal pulse of Fe⁵⁹ was compared to the distribution of FE⁵⁹ 15 minutes after the pulse. Two mucosal fractions showing increased transfer of Fe⁵⁹ to the carcass in animals with increased iron absorption were identified. It is proposed that these fractions participate in mucosal iron transport, whether as labile pools or carriers remains to be determined.