Hemosiderosis in rodents and the effect of acetohydroxamic acid on urinary iron excretion.

Previously reported animal models of hemosiderosis fall short of simulating the human disease state of transfusion-induced hemosiderosis. An explanation for this was found by reexamining heat-treated red blood cell (rbc) loading in the mouse. After 18 intraperitoneal transfusions, each equal to two-thirds of mouse rbc volume, liver Fe reaches a level of 0.3% Fe (dry weight), which is far below the 2%-8% found in heavily transfused patients. Using the easily synthesized chelate compound ferric acetohydroxamate, Fe(AHA)3, liver Fe levels in the rat of up to 2% were achieved after 38 intraperitoneal injections. Fe was distributed in both the reticuloendothelial (RE) system and parenchymal cells, as ascertained by light microscopy. No definite histological or biochemical abnormalities could be demonstrated in loaded rats. Cardiac Fe was approximately doubled. Thus, chelate loading, while producing Fe liver levels similar to those of humans with hemosiderosis, may still be of limited usefulness in studying long-term sequelae. On the other hand, this model can be used in determining responses to chelating agents. To explore this, Fe stores were first labeled by giving 59Fe as 59Fe(AHA)3 prior to loading. In animals loaded to 0.7% liver Fe (calculated), desferroxamine, at a dose of 400 mg/kg, induced a 20-fold rise in urinary Fe. This was duplicated by AHA at a dose of 800-1600 mg/kg. It is concluded that Fe(AHA)3-loaded rats are a potentially useful model of hemosiderosis and that further studies are needed to determine whether AHA can be effective in the treatment of transfusion-induced hemosiderosis.

Effect of dose, time, and ascorbate on iron excretion after subcutaneous desferrioxamine.

The effect of 12 and 24 h continuous subcutaneous infusion of desferrioxamine (D.F.) on urinary iron excretion was compared in 13 patients with beta-thalassaemia major and 1 with congenital sideroblastic anaemia, all of whom were receiving regular blood-transfusions. 750 mg D.F. given over a 12 h period, gave a mean total (30 h) iron excretion of 17-5 mg, which was not statistically different from the mean iron excretion of 21-5 mg when the same dose was delivered over 24 h. 1500 mg D.F. gave a mean urinary iron excretion of 28-1 mg with a 12 h infusion, which was significantly less than the mean iron excretion of 39-6 mg with 24 h infusion. The 1500 mg dose gave a significant increase in iron excretion compared with the 750 mg dose when given by either 12 h or 24 h infusion. 7 of 8 patients, given D.F. over a 12 h period, had increased iron excretion when the dose was increased from 750 to 2000 mg. When the dose was increased to 4000 mg, however, the effect on iron excretion was variable. On the other hand, ascorbic-acid therapy was invariably associated with increased iron excretion after subcutaneous D.F. In twelve studies at different dose levels of D.F., ascorbate therapy was associated with increased iron excretion ranging from 24 to 245%. It is concluded that in most patients with transfusional iron overload subcutaneous D.F over a 12 h period, at a dose ranging from 2 to 4 g daily with ascorbic-acid saturation, is at present the most satisfactory method of removing excess iron.