Changes in the microcirculation in slow and fast skeletal muscles with long term limitations of blood supply.

STUDY
OBJECTIVE: Long term limitation of blood flow leads to decreased muscle performance and to damage, particularly in predominantly oxidative muscles. This study was performed to assess to what extent such damage can be explained by changes in microcirculation in capillaries supplying glycolytic or oxidative muscle fibres.
DESIGN: Velocity and intermittency of flow, capillary diameters and proportion of adhering leucocytes were measured in capillaries in the epi-illuminated superficial glycolytic layer of rat tibialis anterior and in oxidative soleus muscles five weeks after ligation of the common iliac artery. EXPERIMENTAL MATERIAL: Male Sprague Dawley rats (approximately 350 g) were used, under sodium pentobarbitone anaesthesia. MEASUREMENTS AND
RESULTS: Pressure in the saphenous artery, distal to the ligation site, recovered to 61% of carotid mean pressure. In tibialis anterior with limited blood supply, capillary diameters were narrower, red blood cell velocity was greater and intermittency of flow was reduced, resulting in a calculated volume flow per capillary which was only marginally reduced compared with controls. In soleus with limited blood supply, the time spent stationary by red blood cells was increased and there was a greater adhesion of white blood cells to venular walls. In neither muscle did limitation of blood supply result in a change in capillarity.
CONCLUSIONS: Long term limitation of blood supply does not diminish the capillary density or capillary to fibre ratio of anatomically present capillaries in oxidative or glycolytic muscles and does not affect blood flow in capillaries supplying glycolytic fibres appreciably; circulation in capillaries supplying oxidative fibres is impaired.