EFFECTS OF INHALED NITRIC-OXIDE COMPARED WITH ASPIRIN ON PLATELET-FUNCTION IN-VIVO IN HEALTHY-SUBJECTS

1. Nitric oxide has platelet-stabilizing effects. Inhaled nitric oxide is used to treat pulmonary disorders, and may prolong bleeding times, suggesting that it has effects on haemostasis, We therefore examined if inhaled nitric oxide influences platelet function in vivo in health y subjects. 2. Platelet aggregability (filtragometry ex vivo, which re flects aggregability in vivo), bleeding time and platelet secretion pr oducts and cGMP in plasma were studied during inhalation of two differ ent doses of nitric oxide (30 and 80 p.p.m.; 15 min at each dose level ; n=19) and during prolonged (55 min; n=18) inhalation of 30 p.p.m. ni tric oxide. For comparison, studies were also performed before and aft er ingestion of 640 mg aspirin in 13 of the healthy subjects, 3. Plasm a cGMP increased dose dependently during nitric oxide inhalation, sugg esting guanylate cyclase activation in vivo, Platelet aggregability wa s, however, little affected and platelet secretion was not attenuated by nitric oxide inhalation, Bleeding time tended to increase (by 16-33 %), but was significantly increased only after prolonged inhalation of nitric oxide at 30 p.p.m. 4. Aspirin (640 mg orally) caused pronounce d and significant prolongations of filtragometry readings and bleeding time. Thus, the methods used were able to reveal platelet stabilizati on. 5. We conclude that nitric oxide inhalation causes only mild, if a ny, attenuation of platelet function in with a normal endogenous nitri c The effects may be different in healthy oxide production, disease st ates.