Role of Hyperreactivity of Bronchial and Pulmonary Vascular Muscle to Acetylcholine and Histamine in Anaphylactic Shock in Rabbits and Guinea-pigs.

Liberation of excessive amounts of acetylcholine (ACh) has "been considered by DANItLOPOLU (1 to 3) as the dominant factor-in triggering pathogenic mechanisms in anaphylactic shock (AS), serum sickness, asthma and other pathological conditions associated with antigen-antibody reactions. In agreement with DANILOPOLU'S hypothesis, WENNER AND BUHRMESTER (4) reported an increase of ACh in the blood of sensitized and shocked rabbits. However, KOURILSKY, GUILLOT AND GwAN (5) and RATNOFF (6) questioned the importance of ACh in AS because they failed to detect increased amounts of ACh in shocked tissues or in the body fluids of various shocked animals. Failure to detect excessive amounts of ACh would not preclude the hypothesis that ACh plays a dominant role in the pathogenesis of AS if we assume that the pathogenic factor is hyperreactivity to amounts of ACh normally present in tissues, rather than liberation of an excess of ACh. Hyperreactivity of pulmonary vascular muscle to small doses of ACh can be induced by an extrinsic agent such as endotoxin (7), and its role in the pathogenesis of endotoxin shock has been investigated (8). Hyperreactivity of bronchial smooth muscle to ACh and, to a lesser degree, to histamine, has been reported in asthmatic patients (9 to 10).