The effect of iron overload on urinary excretion of immunoreactive prostaglandin E 2

Abstract

The effect of in vivo lipid peroxidation on the excretion of immunoreactive prostaglandin E 2 (PGE 2) in the urine of rats was studied. Weanling, male Sprague-Dawley rats were fed a vitamin E-deficient diet containing 10% tocopherol-stripped corn oil (CO) or 5% cod liver oil (CLO) with or without 40 mg dl-α-tocopheryl acetate/kg. To induce a high, sustained level of lipid peroxidation, some rats were injected intraperitoneally with 100 mg of iron as iron dextran after 10 days of feeding. Iron overload stimulated in vivo lipid peroxidation in rats, as measured by the increase in expired ethane and pentane. Dietary vitamin E reversed this effect. Rats fed the CLO diet excreted 9.5-fold more urinary thiobarbituric acid-reactive substances (TBARS) than did rats fed the CO diet. Iron overload increased the excretion of TBARS in the urine of rats fed the CO diet, but not in urine of rats fed the CLO diet. Dietary vitamin E decreased TBARS in the urine of rats fed either the CO or the CLO diet. Iron overload decreased by 40% the urinary excretion of PGE 2 by rats fed the CO diet, and dietary vitamin E did not reverse this effect. Iron overload had no statistically significant effect on urinary excretion of PGE 2 by rats fed the CLO diet. A high level of lipid peroxidation occurred in iron-treated rats, as evidenced by an increase in alkane production and in TBARS in urine in this study, and by an increase in alkane production by slices of kidney from iron-treated rats in a previous study [ V. C. Gavino, C. J. Dillard, and A. L. Tappel (1984) Arch. Biochem. Biophys., 233, 741–747]. Since PGE 2 excretion in urine was not correlated with these effects, lipid peroxidation appears not to be a major factor in renal PGE 2 flux.