Figure 2. ACE2 and renin levels in mouse hearts, brains, lungs, and kidneys isolated from young and old animals. Adult mouse hearts were sectioned following the following anatomy: ventricular parts (V), atrium (A), and vessels associated with the aorta (AO). The levels of selected proteins were studied by western blotting, and the data were normalized to the total protein levels. The level of the ACE2 protein was examined in (A) mouse hearts, (B) brains, (C) lungs, and (D) kidneys isolated from young and old male and female mice. Quantification was performed using ImageJ software. Red asterisks indicate a decrease in the protein level; blue asterisks show a high ACE2 protein level compared with other samples analyzed in panel B. The nonparametric Mann–Whitney test was used for statistical analysis. Asterisks (*) indicate α=0.05.