Fig. 1

Cardiopulmonary bypass reduces oxidative stress both in cardiomyocytes and in non-cardiomyocytes in newborns. The level of the oxidative stress in the myocardium was assessed by the immunostaining for 8-hydroxy-guanosine (8-dOHG). The percentage of 8-dOHG⁺ cardiomyocytes (a) and 8-dOHG⁺ non-cardiomyocytes (d) was significantly reduced in the newborns (n = 4) but not in the children (n = 7) after interventions using the heart–lung machine. There was no statistical difference in the percentage of 8-dOHG⁺ cardiomyocytes (b) and 8-dOHG⁺ non-cardiomyocytes (e) in the biopsies from the atrium and ventricle of children, n = 3 per group. Decrease (ΔCPB) in the percentage of 8-dOHG⁺ cardiomyocytes (c) and 8-dOHG⁺ non-cardiomyocytes (f) was more pronounced in newborns. Cardiomyocyte density per mm² was not changed after cardiopulmonary bypass both in the newborns (n = 4) and the children (n = 7) (h). Cardiomyocyte density was similar in the biopsies from atrium and ventricle of children (n = 3) (i). Representative sections from the atrium of a newborn before and after cardiopulmonary bypass demonstrating co-immunostaining for 8-hydroxyguanosine (red) and cardiomyocyte marker alpha-sarcomeric actin (green) (g) and immunostaining for alpha-sarcomeric actin (green) (j). Nuclei are stained blue by DAPI. Bars = 10 µm