Effects of angiotensin II and bradykinin on isolated human pulmonary arteries.

In vitro studies were performed on the contractile responses of 44 human segmental pulmonary artery specimens obtained from 26 patients undergoing thoracic surgery for pulmonary malignancies or bronchiectasis. Isometric changes in tension were recorded as cumulative dose-response curves in 14 arterial strips after angiotensin II. The angiotensin II-antagonist (Sar1, Ile8-)-angiotensin II demonstrated a competitive antagonism to angiotensin II. No changes of the resting tension occurred from a steady state in 10 specimens after bradykinin challenge. The relaxing effect of bradykinin was investigated after maximal contraction with either prostaglandin F2 alpha, histamine or norepinephrine in 23 specimens. Some relaxation could be obtained in 18, but total relaxation did not occur. We postulate the presence of specific angiotensin II-receptors mediating weak contraction and bradykinin-receptors mediating weak relaxation in isolated human pulmonary arteries.