Capillary density and muscle fibre size in the hearts of rats subjected to stimulated high altitude.

Six Wistar rats were subjected to a barometric pressure of 50.7 kPa (380 mmHg) for 34 days. These rats and six controls were killed and their myocardial capillaries perfused with India ink. Hypoxia did not induce any proliferation of capillaries in the left ventricle neither did it lead to a reduction in myofibre size. In the right ventricle the capillary density was reduced largely due to a two-fold increase in myofibre area but there was an increase in the capillary: fibre ratio indicating a modest proliferation of capillaries secondary to right ventricular hypertrophy.