Effects of vasodilators on filtration coefficient and distal arterial pressure in muscle

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Abstract
Acetylcholine, isoproterenol, or histamine was infused intraarterially into the gastrocnemius-soleus muscles of the cat while blood flow was held constant and the muscles were intermittently and maximally stimulated to contract isometrically. Acetylcholine depressed muscle force and capillary filtration coefficient (CFC), and elevated the "distal" pressure in a branch of an artery supplying the muscle. Isoproterenol and histamine produced smaller decreases in force and no detectable changes in CFC and distal pressure. The effect of isoproterenol and histamine on muscle force may be due to redistribution of blood flow among parallel vascular channels in the muscle. Acetylcholine may have a similar action, but in addition appears to produce a constriction of arteriolar on precapillary elements which reduces the number of capillaries being perfused.