ENDOGENOUS VASODILATORS MODULATE PULMONARY VASCULAR ANAPHYLAXIS

Endogenous vasodilators modulate pulmonary vascular anaphylaxis. J. Ap pl. Physiol. 76(2): 916-922, 1994. - We examined the role of endotheli um-derived nitric oxide during antigen-induced contraction in pulmonar y arteries isolated from actively sensitized guinea pigs. Ovalbumin (1 0(-2) mg/ml)-induced contraction was not sustained, and tension return ed to baseline within 15 min. Pretreatment with methylene blue (10(-5) M) increased both the amplitude and the duration of the contractile r esponse in these tissues. At 15 min, tension remained elevated and was >70% of the peak amplitude. Removal of the endothelium with saponin ( 200 mu g/ml) increased the magnitude of the contraction by >125%; howe ver, the duration of the response was unaffected. After pretreatment w ith saponin, methylene blue no longer increased the amplitude of antig en-induced contraction but its effect on the duration was unchanged. P retreatment with nitro-L-arginine methyl ester significantly increased the magnitude of the contraction in each of the tissues. These result s suggest that the response of guinea pig pulmonary arteries to antige n is modulated by two types of endogenous vasodilators, endothelium-de rived nitric oxide that inhibits the initial phase of the response and an endothelium-independent relaxing factor that is guanosine 3', 5'cy clic monophosphate dependent and attenuates the duration of anaphylact ic contraction.