Age-Related Myocardial Histopathology and Desmin-Associated Intercalated Disc Changes After Exercise

Background: The myocardial response to repeated physical loading may vary with age, and structural changes may not be captured by functional measurements alone. This experimental study examined myocardial histopathology and desmin-associated intercalated-disc morphology in rats of different ages exposed to distinct exercise protocols. Methods: Male white laboratory rats were assigned by age to a control group or one of three exercise groups: treadmill exercise, 40-minute swimming with a tail load equal to 2% of body mass, or 60-minute swimming with a tail load equal to 4% of body mass. Histological assessment included hematoxylin and eosin staining, Masson’s trichrome staining, and immunohistochemical evaluation of desmin. Results: The dissertation describes more prominent changes in the anterior wall of the left ventricle than in the lateral wall. Findings included vascular hyperemia and congestion, stasis, focal vascular-wall injury, cardiomyocyte degeneration and fragmentation, and perivascular/interstitial fibrosis. Intercalated-disc frequency was reported as 22.50% versus 22.33% in young experimental and control rats, 24.17% versus 22.67% in middle-aged rats, and 23.67% versus 25.67% in older rats. Conclusions: The findings suggest age- and protocol-associated variation in myocardial structural response. Because full quantitative scoring and endpoint-specific inferential statistics are not available in the extracted text, the observations are descriptive.