Increased capillary density due to atrophy of ischaemic soleus muscle of the rat.

This investigation was undertaken to determine whether a severe limitation of blood supply by external iliac artery ligation can change the number and density of capillaries in rat soleus muscle. The external iliac artery in one hindlimb was ligated for 2, 7 or 28 days, and the other, sham-operated, hindlimb was used as a control. Muscle blood flow in the ischaemic soleus muscle at 2, 7 and 28 days after external iliac artery ligation was significantly decreased compared with the control. The muscle fibre area and the ratio of the fibre area to body mass in the ischaemic soleus muscle at 28 days after the external iliac artery ligation were significantly reduced in the ischaemic soleus muscle, but no change in the number of capillaries per fibre was observed. Capillary density per millimetres squared at 28 days and the ratios of the number of capillaries around type I fibres to the fibre area at 7 and 28 days were significantly increased in the ischaemic soleus muscle (P < 0.05). These results suggested that long-term severe limitation of blood flow in the soleus muscle by ligation of the external iliac artery could have induced the increase in capillary density, as a result of atrophy of muscle fibres rather than capillary growth.