Modulation of uptake of heme by rat small intestinal mucosa in iron deficiency

Although body iron status modulates whole body retention of heme derived iron, it is not known with certainty whether modulation occurs by regulation of mucosal uptake of heme. In vivo uptake from perfused intestine of heme labeled with 14C in the porphyrin ring was studied in groups of rats of differing iron status ranging from fully replete to markedly iron deficient. Heme extraction from infusate and mucosal heme uptake were significantly different between test groups (P < 0.005 and 0.001, respectively). Marked iron deficiency induced a 4.8-fold rise in heme extraction relative to iron-replete animals; rats with latent iron deficiency showed a smaller but still significant rise. Heme extraction correlated negatively with indicators of iron status: hemoglobin (r = -0.76, P < 0.001) and serum iron (r = -0.56, P < 0.05). The specific binding of [14C]heme to purified brush borders from iron-replete and iron-deficient rats was 1.4-fold higher in deficient rats when expressed per milligram of protein (P = 0.046) and 3.3-fold higher when expressed relative to alkaline phosphatase activity (P = 0.014). Thus mucosal uptake of heme in iron deficiency is increased because of an increase in its binding to the brush border.