Ultrastructural studies of the myocardium of rats on low-magnesium diet treated with cyclophosphamide.

Cyclophosphamide administration in 20 mg/kg doses intraperitoneally at intervals of 6 days for 6 weeks produced the appearance of slight focal changes in myocardial fibres from the third week on, with dilatation of T-tubules and smooth endoplasmic reticulum channels with electron-dense deposits in them, with the appearance of numerous fat droplets in myocardial fibres, slight mitochondrial changes, with swelling and the appearance of giant or bizarre shaped mitochondria with electron-dense granules and lamellae in them, with numerous lysosomes and some increase in the number of autophagosomes, focal widening of intercalated discs, lysis of myofilaments and myofibrils, cytoplasm swelling, focal necrosis of some myocardial fibres in the 6th week of the experiment, marked swelling of vascular endothelial cells, and a very great rise in the number of collagen fibres. Simultaneous administration of low-magnesium diet and cyclophosphamide caused a greater intensity and an earlier appearance from the 2nd week on, of the disseminated degenerative and necrotic changes in myocardial fibres.