Identification of presynaptic β2‐adrenoceptors on the sympathetic nerve fibres of the human pulmonary artery

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Abstract
1 Strips of human pulmonary arteries from patients undergoing surgery for lung tumour were incubated with [3H]-noradrenaline. Subsequently, they were supervised with physiological salt solution containing cocaine and corticosterone. Tritium overflow from the strips was stimulated by transmural electrical impulses (2 Hz). The electrically evoked overflow of tritium consisted of 91% unmetabolized [3H]-noradrenaline, and this percentage was not altered by isoprenaline. 2 Adrenaline (in the presence of rauwolscine), isoprenaline and the preferential β2-adrenoceptor agonist, procaterol, concentration-dependently increased the electrically evoked tritium overflow. Prenalterol, a β-adrenoceptor agonist with moderate preference for β,-adrenoceptors, was considerably less active than the previously mentioned agonists; noradrenaline (in the presence of rauwolscine) was ineffective. 3 The concentration-response curve of procaterol was shifted to the right by the preferential β2-adrenoceptor antagonist ICI 118–551 but was not affected by the β1-selective antagonist, atenolol. Propranolol, but not atenolol, produced a shift to the right of the concentration-response curve of isoprenaline. 4 It is concluded that the sympathetic nerve fibres of the human pulmonary artery are endowed with facilitatory presynaptic β2-adrenoceptors.
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