Morphological changes in myocardium of Wistar rat caused by hyperthermia

Objectives: Aim of our study was to examine whether the intensity of myocardial changes in Wistar rats exposed to hyperthermia was related to the temperature and to classify the degree and type of cardiomyocyte damage. Methods: The study was conducted on 40 adult Wistar rats that were methodologically divided into groups, depending on water temperature exposure of 37 °C (n = 8), 41 °C (n = 16), and 44 °C (n = 16). Depending on the length of the water temperature exposure time of 41 °C and 44 °C, rats were divided into antemortem (water temperature exposure 20 min) and postmortem groups (water temperature exposure to death). Myocardial sample for pathohistological analysis was taken after the death of the animal. Microscopic examination with semiquantitative analysis of myocardial changes was performed. Results: Pathohistological analysis determined the normal myocardial structure of control group (animals exposed to water temperature of 37 °C, with mild, degenerative changes in cardiomyocytes nonspecific for hypertemia in rats exposed to water temperatures of 41 °C and 44 °C. Type of myocardial changes in rats in groups exposed to water temperatures of 41 °C and 44 °C was classified as minimal and multifocal degenerative changes (45.25 %; 51.6 %, respectively), which was significantly more pronounced compared to the myocardial control group (p < 0.0005). Conclusion: The dynamics of the development of morphological changes in cardiomyocytes did not show high significance, which is attributed to the short manifestation time, and does not make it impossible to visualize changes at the subcellular level in tissuestained by hematoxylin-eosin method