PATTERN OF CARDIAC FIBROSIS IN RABBITS PERIODICALLY FED A MAGNESIUM-RESTRICTED DIET AND ADMINISTERED RARE-EARTH CHLORIDE THROUGH DRINKING-WATER

It has been postulated that causation of the tropical cardiomyopathy e ndomyocardial fibrosis (EMF) is linked to magnesium (Mg) deficiency an d cardiac toxicity of the rare earth element cerium (Ce). The aim of t he present study was to define the myocardial lesions in rabbits that were fed on Mg-restricted diet (70-80 ppm) periodically and were provi ded drinking water contaminated with rare earth chloride (1 g/L). Fort y New Zealand white rabbits were divided into four groups following a 2 x 2 factorial design. Two groups were periodically fed on Mg-restric ted diet with one of them receiving water contaminated with rare earth chloride. The other two groups were continuously fed on Mg-sufficient diet (350-400 ppm) with one of them receiving water contaminated with rare earth chloride. AU animals were sacrificed at the end of 6 mo. C ardiac tissues were subjected to histology, elemental analysis (calciu m [Ca], Mg, and Ce) and estimation of collagen content and collagen ph enotypes. Histological lesions were compared with those of EMF in huma ns and those of acute Mg deficiency in animals. The results suggest th at in rabbits, recurrent episodes of Mg deficiency lead to myocardial fibrosis similar to the pattern observed in human EMF.