Fig. 3

Myocardial fibrosis, capillary density, and electron microscopic imaging. Representative images of myocardial sections stained with picrosirius red and Mayer’s hemalum in all groups. The colour red identifies fibrosis. a The fibrotic area in the heart samples was significantly larger in the D-CON and AA groups compared to CON, while the BB and ACEI treatments significantly decreased the level of fibrosis compared to that in the D-CON group. a, b When analysing the capillary density of the myocardial sections, no statistically significant differences could be identified between the groups. c Electron microscopic images displayed robust ultrastructural changes in the myocardium of the D-CON animals (apoptotic cardiomyocytes, vacuolisation, mitochondrial damage, myofibrillolysis), leading to a decreased overall density of the acquired images compared to CON. Images taken in the groups receiving any prophylactic treatment showed significantly less ultrastructural damage compared to D-CON. d, e DOX exposure resulted in a tendency for the development of cardiomyocyte hypertrophy, which was the most apparent in the AA group. The ACEI treatment successfully prevented this change and cardiomyocyte diameters remained small in that group. f n = number of animals per group (9 images per animal for fibrosis, 1–5 images per animal for capillary density, 2–5 pictures per animal taken at the level of the nucleus for cardiomyocyte diameter measurements, 1–3 pictures per animal for densitometry); Statistics: Wilcoxon’s rank-sum test; numbers are p values. AU = optical density in arbitrary units