INCREASED RESPONSIVENESS OF HUMAN PULMONARY-ARTERIES IN PATIENTS WITHPOSITIVE BRONCHODILATOR RESPONSE

1 The effects of noradrenaline, endothelin-1, acetylcholine and sodium nitroprusside were studied in isolated pulmonary arteries obtained fr om 14 patients undergoing lobectomy for lung carcinoma. Seven patients had shown increased response to a bronchodilator test prior to operat ion. In the remaining patients (control) the bronchodilator test was n egative. 2 Artery rings from patients with a positive bronchodilator r esponse showed greater contraction to noradrenaline (pD(2) = 6.44 +/- 0.1; E(max) = 93 +/- 9% of response to 100 mM KCl) and endothelin-1 (p D(2) = 8.92 +/- 0.1; E(max) = 130 +/- 16%) than the rings from control patients (pD(2) = 6.04 +/- 0.08; E(max) = 56 +/- 8% for noradrenaline ; pD(2) = 8.29 +/- 0.1; E(max) = 78 not equal 10% for endothelin-1). T here was no significant difference in the contractile responses to 100 mM KCl between arteries from either group of patients. 3 Arterial rin gs from patients with a positive bronchodilator test achieved 96 +/- 3 % of maximal relaxation in response to acetylcholine, whereas rings fr om control patients achieved a maximal relaxation of 72 +/- 5%. Rings from botb the controls and the patients with a positive bronchodilator test achieved complete relaxation in response to sodium nitroprusside but pD(2) values were significantly higher in patients with a positiv e bronchodilator test. 4 Removal of endoghelium or treatment with N-G- nitro-L-arginine methyl ester of artery rings from both the control an d the patients with a positive bronchodilator test reduced the relaxat ion to acetylcholine (P < 0.05) but did not modify relaxation to sodiu m nitroprusside. 5 It is concluded that responsiveness of pulmonary ar terial smooth muscle to dilator and constrictor agents is increased in patients showing reversibility of airway constriction. Thus hyperresp onsiveness of airway smooth muscle may be associated with a similar ph enomenon in the surrounding vascular smooth muscle.