The impact of daily work load during pregnancy and/or postnatal life on the heart microstructure of rat male offspring.

The microstructure of the cardiac muscle of four groups of male rats was investigated: control (EC) and exercised (EE) offspring of mothers exercised during pregnancy, and control (CC) and exercised (CE) offspring of inactive control mothers. The differences between groups were subjected to variance analysis and multiple range testing according to Duncan. Total body weight did not differ during the entire experiment. With the exception of the subgroup CE (lower values) the absolute and relative (mg/100 g total B.W.) weight of the cardiac muscle did not differ either. The number of heart fibres and capillaries per mm2 was highest in subgroup EE, and significantly lowest in subgroup CC. The capillary: fibre ratio was significantly highest in EE; diffusion distance (D/2) was shortest in EE. Other groups were intermediate. A greater impact of prenatal than postnatal work load on the microstructure of the cardiac muscle of the offspring was demonstrated.