Adrenergic receptors and sympathetic agents in isolated human pulmonary arteries.

We tested the in vitro contractility of 88 segmental pulmonary arteries from 46 patients undergoing thoracic surgery. The vascular strips, taken from macroscopically healthy lung tissue, were devoid of spontaneous adrenergic tone. Cumulative dose-response curves with epinephrine and norepinephrine showed graded contraction. There was no significant difference between the two substances concerning mean maximal tension, threshold doses, ED50 or concentrations causing maximal contraction. Alpha-receptor blocking agents, phenoxybenzamine and indoramine, showed an inhibition of the contraction induced with both epinephrine and norepinephrine. Epinephrine in higher doses caused a dual response: contraction followed by relaxation. The latter was blocked by propranolol. Both isoproterenol and theophylline relaxed contracted vessels to some extent. Relaxation induced by isoproterenol could be blocked by propranolol. "Selective" beta2-stimulants such as terbutaline or salbutamol induced no relaxation. The results suggest the presence of alpha-receptors mediating constriction and possibly beta1-receptors mediating relaxation in human segmental arteries.