Kinetic analysis shows that iron deficiency decreases liver vitamin A mobilization in rats

In view of evidence that nutritional status of iron and vitamin A may affect the other nutrient's metabolism, we used model-based compartmental analysis to examine effects of iron deficiency on whole-body vitamin A dynamics in rats, Weanling male Sprague-Dawley rats were fed the AlN93G diet with 2.5 nmol retinyl palmitate/g and either 45 [control (CN)] or 4 mu g/g Fe [iron-deficient (ID)] for 8 wk. to rats consumed food ad libitum; CN rats were food-restricted so that their body weights were the same as ID rats. Two rats/group were killed; liver vitamin A was determined and used for vitamin A balance calculations, [H-3]Retinol-labeled plasma was administered intravenously to remaining rats, and 27 serial blood samples were collected for 7 wk. At killing, plasma vitamin A was 0.52 +/- 0.12 (ID, n = 5) vs. 1.34 +/- 0.12 mu mol/L (CN, n = 6; P < 0.001), and liver vitamin A was 809 +/- 94 (ID) vs. 112 +/- 24 nmol (CN, P < 0.001). Plasma tracer data were fit to a three- or four-compartment model using the Simulation, Analysis and Modeling computer program and kinetic parameters were calculated. Vitamin A transfer rate between the retinyl ester storage pool [14 +/- 3 (ID) vs. 24 +/- 4 nmol/d (CN), P < 0.05] and plasma was lower in ID rats. Vitamin A remained longer in the body [44 +/- 11 (ID) vs. 22 +/- 3 d (CN), P < 0.05]. Adjusted mean disposal rate was lower in ID (10.0) than CN rats (19.9 nmol/d), as was estimated vitamin A absorption efficiency [58% (ID) vs. 76% (CN)], Our results suggest that iron deficiency inhibits mobilization of vitamin A stores and may decrease the absorption and irreversible utilization of vitamin A.