The analysis of the histopathological characteristics of the control untreated group of young male rats showed that the myocardium structure of both the left and right ventricles corresponded to the histological norm. With hematoxylin and eosin staining, the histoarchitecture of the cardiac muscle in all histological sections of all animals was preserved (Table 1). Rows of cardiomyocytes without hypertrophy, significant eosinophilia, or cross striation were identified, with a centrally located basophilic oval vesicular nucleus (Figure 7). With Masson’s trichrome staining, a small amount of collagen fibers was observed in the perivascular space, predominantly located in the vessel wall (Table 1). Collagen fibers were mostly absent in the interstitial space. In individual fields of view of some sections, threadlike thin and short blue collagen fibers were noted (Figure 7).