Perturbed Vitamin A Status Induced by Iron Deficiency Is Corrected by Iron Repletion in Rats with Pre-Existing Iron Deficiency

Background: Although iron deficiency is known to interrupt vitamin A (VA) metabolism, the ability of iron repletion to restore VA metabolism and kinetics in iron-deficient rats is not well understood. Objectives: In the present study, we examined the effects of dietary iron repletion on VA status in rats with pre-existing iron deficiency. Methods: Weanling Sprague-Dawley rats were fed a VA-marginal diet (0.35 mg retinol/kg diet) containing either a normal concentration of iron [35 ppm, control group (CN)] or reduced iron (3 ppm, iron-deficient group, ID-); after 5 wk, 4 rats/group were killed for baseline measurements. A H-3-labeled retinol emulsion was administered intravenously to the remaining rats (n = 6, CN; n = 10, ID-) as tracer to initiate the kinetic study. On day 21 after dosing, n = 5 ID- rats were switched to the CN diet, generating an iron-repletion group (ID+). Blood samples were collected at 34 time points <= 92 d after dose administration, when all rats were killed and iron and VA status were determined. Results: At baseline, ID- rats had developed iron deficiency, with a reduced plasma VA concentration (0.67 compared with 1.20 mu mol/L in ID- and CN rats, respectively; P < 0.01) and a tendency toward higher liver VA (265 compared with 187 nmol in ID- and CN rats, respectively; P = 0.10). On day 92, iron deficiency persisted in ID- rats, accompanied by 2-times higher liver VA (456 nmol compared with 190 nmol in ID- and CN rats, respectively; P < 0.001) but lower plasma VA (0.64 compared with 0.94 mu mol/L in ID- and CN rats, respectively; P = 0.05). ID+ rats not only recovered from iron deficiency, but also exhibited less liver VA sequestration (276 nmol) and normal plasma VA (0.91 mu mol/L, not different from CN rats). Conclusions: Our results suggest that iron repletion can remove the inhibitory effect of iron deficiency on hepatic mobilization of VA and restore plasma retinol concentrations in iron-deficient rats, setting the stage for kinetic studies of VA turnover in this setting.