MAGNESIUM DEFICIENCY-RELATED CHANGES IN LIPID-PEROXIDATION AND COLLAGEN-METABOLISM IN-VIVO IN RAT-HEART

Magnesium deficiency is known to produce a cardiomyopathy, characteris ed by myocardial necrosis and fibrosis. As part of the ongoing investi gations in this laboratory to establish the biochemical correlates of these histological changes, the present study probed the extent of lip id peroxidation and alterations in collagen metabolism in the heart in rats fed a magnesium-deficient diet for 28, 60 or 80 days. While lipi d peroxidation was measured by the thiobarbituric acid reaction, colla gen turnover rates and fibroblast proliferation were assessed using [H -3]-proline and [H-3]-thymidine, respectively. Tissue levels of magnes ium and calcium were determined by atomic absorption spectrophotometry . A 39% increase in the cardiac tissue level of thiobarbituric acid re active substances was observed on day 60 of deficiency (p < 0.001). A marked drop in collagen deposition rate (59%, p < 0.001%) on day 28 bu t a significant rise in fractional synthesis rate (12%, p < 0.001) and collagen deposition rate (24%, p < 0.001) on day 60 were observed. A fibroproliferative response in the heart was evident on day 80 but not at earlier time-points. Thus, the present study provides evidence of increased lipid peroxidation and net deposition of collagen in the myo cardium in response to dietary deficiency of magnesium. These changes were, however, not directly related to alterations in the tissue level s of Mg. It is suggested that the increase in cardiac collagen synthes is and fibroplasia associated with Mg deficiency may represent reparat ive fibrogenesis, upon oxidative damage to the cardiac muscle, and is mediated by a mechanism independent of changes in cardiac tissue level s of Mg. (C) 1997 Elsevier Science Ltd.