DIETARY IRON AND FAT AFFECT NONHEME IRON-ABSORPTION, IRON STATUS, ANDENTEROCYTE ACONITASE ACTIVITY AND IRON CONCENTRATION IN RATS

The cytosolic iron regulatory protein 1 (IRP1) exhibits aconitase (c-a con) activity when it is iron loaded. Enterocyte c-acon activity may b e an index of IRP1 activity and important in the regulation of iron me tabolism and absorption. Because stearic acid (SA) can enhance iron ab sorption the relationship between absorption and enterocyte c-acon act ivity in iron-deficient rats fed different types and amounts of dietar y fat was determined. Rats (8/group) were fed diets varying in iron (1 0 or 35 mu g/g), fat type [SA, safflower oil (Saff, cocoa butter (CB), or beef tallow (BT)] and fat amount (7 or 15%). Rats killed for basel ine values were iron-deficient with low enterocyte c-acon activity. Ab sorption was assessed by Fe-59 retention. After 4 wk, Delta Hb and c-a con activity were less (p<0.001) and iron absorption was greater (p<0. 001) in rats fed low dietary iron (10 mu g/g) than in rats fed adequat e dietary iron (35 mu g/g). Absorption was greater (p<0.05) in SA-, CB - and BT- than Saff-fed rats fed a low iron diet. Enterocyte cytosolic and total cellular iron were less (p<0.001) in rats fed low versus ad equate dietary iron, In rats fed adequate iron, total cellular iron wa s dependent (p<0.01, r(2)=0.59) on liver and serum iron concentrations . Low dietary iron (10 mu g/g) resulted in iron deficiency, higher abs orption, and lower enterocyte c-acon activity and iron concentration t han adequate dietary iron (35 mu g/g). This suggests that enterocyte c -acon activity may be an index of IRP1 activity and important in enter ocyte cellular iron metabolism and absorption.