Reciprocal changes of muscle oxidases and liver enzymes with recovery from iron deficiency

We determined the recovery time courses of muscle oxidases and liver enzymes after iron administration to iron-deficient rats. Female 21-day-old Sprague-Dawley rats were fed an iron-deficient (3 mg Fe/kg) or a control (50 mg Fe/kg) diet for 3 wk. The deficient rats were then injected with 50 mg Fe as iron dextran/kg body wt (Fe^-T) or saline (Fe^-) intraperitoneally. At 16, 40, 64, 112, and 180 h after injection, blood and tissue samples were taken to determine hemoglobin concentation (Hb), gastrocnemius glycolytic enzyme and oxidase activities, and liver amino acid catabolic enzyme activities. No changes were observed in any parameter across time in either the Fe^- or control (Fe⁺) rats. In the Fe^- rats, Hb, pyruvate + malate (P + M), 2-oxoglutarate (2-OG), and succinate oxidases (SO) were depressed to 33, 36, 44, and 7% of Fe⁺, respectively (P < 0.05). At 16 h, Fe^-T values were significantly elevated compared with Fe^- rats but still only 40, 48, 55 and 10% of controls, respectively. Glutamate dehydrogenase (GDH) and alanine amino-transferase (AAT) of Fe^- rats were 174 and 134% of control values (P < 0.05). By the 180-h time point, Hb, P + M, 2-OG, and SO of Fe^-T rats increased to 99, 84, 89, and 43% of Fe⁺ values, whereas GDH and AAT activities declined to 111 and 106% of controls. Glycolytic enzymes showed no systematic changes with iron deficiency or after iron administration. Altered enzyme profiles in Fe^- rats allows a shift in metabolism to one that is more glycolytic and gluconeogenic than in Fe⁺ animals. During iron repletion both muscle oxidases and liver amino acid catabolic enzymes approach control values indicating a shift to greater dependence on oxidative metabolism by rats recovering from iron deficiency.