Evidence that bile salts are important for iron absorption

Abstract

The role of bile salts in intestinal Fe absorption has not previously been defined. We have recently shown that bile salts having cholanic ring 7 alpha-OH and/or 12 alpha-OH groups bind Fe2+ with high affinity at premicellar concentrations and also produce a two-to threefold enhancement in Fe2+ uptake from perfused intestinal segments in vivo. However, the physiological relevance of these observations for Fe2+ absorption was not known. To study this, we examined the effects of a single dose of taurocholate (TC) administered with 59Fe-FeSO4 in reversing iron malabsorption induced by bile duct ligation. Fe absorption from three 0.5-mg doses of 59Fe-FeSO4 was measured from five groups of six adult Sprague-Dawley rats each: group 1, before and after bile duct ligation and subsequent administration of 59Fe-FeSO4 + TC test dose; group 2, before and after bile duct ligation followed by a third dose of Fe alone; group 3, before and after bile duct ligation followed by a third dose of Fe+taurodehydrocholate (TDHC); group 4, sham laparotomy; and group 5, nonoperated controls where Fe absorption was measured from three doses of 59Fe-FeSO4 at the same time intervals as group 1. Absorption was measured, using whole body counting, after achievement of steady-state counts after each Fe dose. Mean percentage absorption from dose 1 (baseline) was 35.33 +/- 4.6% (SE). No significant differences between any groups were noted. In nonoperated controls (group 4), Fe absorption was virtually identical after all three doses. Also, hematocrit did not change in any of the 30 animals.(ABSTRACT TRUNCATED AT 250 WORDS)