ULTRASTRUCTURAL-CHANGES IN ATRIAL TISSUE OF YOUNG AND AGED RATS SUBMITTED TO NOISE STRESS

Young and senescent rats were exposed to audiogenic stress for 6 h run ning and the effects of the treatment on the atrial myocardium were ev aluated. In both young and senescent animals subcellular alterations o f atrial cardiomyocytes were seen, consisting mainly of changes at the mitochondrial level. In particular, sections from young treated rats exhibited swollen mitochondria with lysis of their cristae and dissolu tion of the matrix. An enlargement was observed of the space between t he outer and inner membranes of the mitochondria, which also showed an increase in size. In addition, aged treated specimens revealed decrea sed density of the sarcoplasm and marked heterogeneity in the myofibri l pattern with ruptures and loss of continuity of the myofilaments.