Abstract
The effect of an ischemic exercise on venous outflow, hematocrit, total plasma protein and plasma crystalloid osmolality through microcirculation in skeletal muscle were investigated in the 'in situ' hindlimb preparation of anesthetized rabbits. A partial ischemic exercise was produced by electrical stimulation of sectioned sciatic nerve end during a 5-min occlusion of the femoral artery, and venous outflow from the muscle was measured by a photocell drop-counter equipped with a D-A converter. A spontaneous input pressure of the femoral artery into the hindlimb was observed to be kept constant during a series of experiment. Results observed are as follows : 1) A 40-60% decrease of venous outflow was observed following the occlusion of the femoral artery. During 5-min occlusion, the normalized change of Hct (the ratio (%) of Hct against pre-occlusion Hct) was 98.6% at the early stage, 102.4% at the final stage and 105.3% after the release of occlusion, respectively. Normalized plasma protein was 97.5% and 102.3% at the early stage and after the release, respectively. Osmolality showed no significant change during 5-min occlusion. 2) The maximal percent change of Hct produced by the ischemic exercise at 5 Hz muscular contraction was 108.8% and 111.3% at 50 Hz. Normalized plasma protein was 113.2% at 5 Hz and 121.5% at 50 Hz, and osmolality was 111.0% at 5 Hz and 113.0% at 50 Hz, respectively. The changes of Hct, protein and osmolality observed during the ischemic exercise were significantly higher than those observed during the non-ischemic exercise. It is suggestive that the increase of Hct during the exercise is caused mainly by the plasma fluid loss from the capillary, and that such hemorheological phenomena as decreased flow rate in the capillary, increased collateral flow and relative decrease of plasma layer to the radius during the ischemic exercise are relatively less effective causes. Much higher increase of protein during the 'severe' exercise may be explained by introducing a speculative such as protein back flux.
