Comparative Effects of Hydralazine, Sodium Nitrite and Acetylcholine on Resistance and Capacitance Blood Vessels and Capillary Filtration in Skeletal Muscle in the Cat

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Abstract
Åblad, B. and S. Mellander. Comparative effects of hydralazine, sodium nitrite and acetylcholine on resistance and capacitance blood vessels and capillary filtration in skeletal muscle in the cat. Acta physiol. scand. 1963. 58. 319—329. — The actions of intra‐arterially infused hydralazine, sodium nitrite and acetylcholine were studied with a technique permitting simultaneous and quantitative recording of the responses in the various ‘series‐coupled’ sections in the skeletal muscle vascular bed. The dilator effects of all three drugs were found to be due to a ‘direct’ action on the vascular smooth muscle. Each of the drugs evoked characteristic peripheral vascular response pattern differentiated from that of the others. Thus, hydralazine dilated the resistance vessels almost exclusively while sodium nitrite predominantly dilated the capacitance vessels. Acetylcholine elicited a pronounced dilatation of both the resistance and the capacitance vessels. Furthermore, hydralazine and acetylcholine produced a net outward capillary filtration into the extravascular space depending upon a relatively more pronounced dilatation of precapillary than post‐capillary resistance vessels, while sodium nitrite did not significantly influence the transcapillary exchange. The present findings may aid in explaining the different general hemodynamic effects elicited by hydralazine and sodium nitrite in the intact organism.