Malondialdehyde binding of rat cerebral proteins is reduced in experimental hypothyroidism

To determine the effect of thyroid hormones (TH) on cerebral tissue malondialdehyde (MDA) content and accumulation of MDA-bound proteins, hyperthyroid rats and hypothyroid rats were compared to euthyroid controls. Hyperthyroidism was induced by daily injection of l-3,5, 3'-triiodothyronine (15 ug (100 g)-1) intraperitoneally daily for 10 days. Hypothyroidism was induced with 0.025% methimazole in the drinking water for 4 weeks. Immunoblot analysis of cerebral and plasma proteins was carried out using a specific anti-MDA-protein antiserum. MDA was measured as thiobarbituric acid reactive substance. Hypothyroidism was associated with significant reduction in MDA-proteins of plasma (59.3+/-9.5% vs. 99.8+/-23.0% of control p<0.05) and cerebral tissue (17.6+/-19.9% vs. 100.2+/-29.0% of control p<0.001). Hyperthyroidism did not significantly alter MDA-protein distribution. These changes did not correlate with cerebral tissue or plasma MDA concentration. It is concluded that hypothyroidism in rats is associated with significant decrease in MDA-bound proteins. This may have some clinical and biological implications.