Blood Flow of Rabbit and Rat Hind Leg Measured by Means of Distribution and Removal of Antipyrine or D2O

The relation between activity and the functional blood flow in the muscle of rabbits and rats was investigated under conditions of anesthesia with nembutal of 35 rng/ kg and electrical stimuli. 2/sec. The magnitude of the distribtion ratio of the muscle, that was the ratio of the concentration of test substance (antipyrine or D20) in muscle water to that of plasma water, and the time to attain equilibration with plasma water were used as indices of the functional blood flow in the tissue. All values obtained from the active muscles were compaired with those of the resting opposite gastrocnemius-soleus muscles. Animals(29 rabbits anb 5 rats) were divided into 4 groups. The first group consisted of 7 rabbits. The distal end of the left sciatic nerve which was cut at the thigh was stimulated for varying period, 3 to 8 minutes. Also sham operation was performed in the opposite side. At the end of stimulation blood samples were taken by cardiac puncture and 5 rnl of saturated KeI was given to induce cardiac arrest. Muscle samples were prepared immediately. At the beginning of the stimulation 200 mg of antipyrine in normal saline was injected intravenously. The second group was 7 rabbits whose nerves of both sides were cut. Otherwise the similar procedure as above was applied. The third group was 5 rabbits and 5 rats. Their nerves were kept intact and direct stimuli were applied. The duration of the stimulation for this group was 6 minutes exclusively. Antipyrine was given intravenously for rabbits and DzO for rats subcutaneously. The fourth group was 10 rabbits which were submitted to bleeding of 30-42 ml prior to the injection of antipyrine. After 30 minutes elapsed which was needed for the equilibration between tissue and blood. the blood diluted with normal saline was reinfused to permit the transport of antipyrine from tissue to blood by creating a concentration gradient. At the same time direct electrical stimulation to the gastrocnemius was begun. Animals were sacrificed 8-24 minutes later. The results obtained were as follows: 1. Blood vessels perfusing the gastrocnemius-soleus muscle of a rabbit are receiving tonic constrictor influence via sciatic nerve. When this nerve was severed prompt rise in the distribution ratio of antipyrine was noticed. suggesting a release from the constrictor influence. 2. When sciatic nerves of both sides were cut and one distal end was stimulated. further increase in flow rate in the active side was appreciable. 3. Contraction of twice per minute could not release completely the blood vessels of the active muscle from the neural constrictor influence. 4. Appling direct stimuli for 6 minutes to the muscle brought about a two-fold increase in the distribution ratio of antipyrine for rabbits and of DzO for rats. comparing with the values of the resting muscles. 5. The desaturation process of antipyrine in rabbits showed an enhanced removal from the active muscle. suggesting a rise in flow rate