A Comparative Study of Β‐adrenoceptors in Human and Porcine Lung Parenchyma Strip

Abstract

1 Responses to (±)-isoprenaline (Iso), (-)-adrenaline (Adr) and (-)-noradrenaline (NA) were compared in isolated preparations of human and porcine lung parenchyma strip. 2 The order of relaxant potencies of these catecholamines in both human and porcine lung parenchyma was Iso > Adr > NA (1:0.24:0.01, human; 1:0.21:0.01, pig). These results suggest that P2-adrenoceptors predominate in both types of lung parenchyma strip. 3 pA2 values for the 1-adrenoceptor antagonist, propranolol (non-selective), with Iso as the agonist, in human and porcine lung strips were 7.84 and 7.83 respectively and for atenolol were 6.50 and 5.35 respectively. Taken as a whole, results indicate the existence of an apparently homogeneous population of P2-adrenoceptors in porcine parenchyma strip, while both PI and P2-adrenoceptors were revealed in human lung parenchyma.

Classification of β‐adrenoceptors in isolated bronchus of the pig

“…While inhibition of extraneuronal uptake with normetanephrine (50 gM) only caused a 2 fold increase in the potency of Iso, it is possible that 1-adrenoceptor blockade caused by normetanephrine partially masked sensitization to Iso (Kenakin, 1980;Goldie & Paterson, 1982 In guinea-pig atria where a homogeneous population of 1l-adrenoceptors also exists (O'Donnell & Wanstall, 1979a,b), the pA2 value for atenolol against Iso was also 7.2 (Harms, 1976). In contrast, in the pig lung parenchyma strip where P2-adrenoceptors predominate, the pA2 value for atenolol against Iso was only 5.4 (Goldie et aL, 1982a). Furthermore, in the present study, salbutamol (32-selective) was a very weak antagonist of Iso-induced relaxation of pig bronchus (pA2 = 4.4).…”

“…In the guinea-pig, P2-adrenoceptors predominate in both central (O'Donnell, 1972;O'Donnell & Wanstall, 1979a) and peripheral airways (Siegl, Rossi & Orzechowski, 1979) while in the cat, there are ladrenoceptors in central airways and 12-adrenoceptors in the peripheral lung strip (Lulich, Mitchell & Sparrow, 1976 (Goldie, Paterson & Wale, 1982a). Thus, it was of interest to characterize the 3-adrenoceptor subtype in bronchial (central) smooth muscle from the pig.…”

“…PI-adrenoceptors in central airways to P2-adrenoceptors in lung parenchyma strip (Goldie et al, 1982a) as there is in the cat (Lulich et al, 1976 …”

Autoradiographic localization of β‐adrenoceptors in pig lung using [125I]‐iodocyanopindolol

“…We have previously shown that P-agonist-induced relaxation of the pig lung parenchyma strip was mediated via P2-adrenoceptors (Goldie et al, 1982). It is often assumed that relaxation of lung strips reflects the reactivity of airway smooth muscle rather than of vascular or alveolar components.…”

“…We have previously shown that P2-adrenoceptors mediate relaxation of the pig lung parenchyma strip (Goldie et al, 1982). However, both Pj-and P2-adrenoceptors have been revealed in both membrane binding studies and in autoradiographic studies in lung parenchyma from the rat (Xue et al, 1983), rabbit (Rugg et al, 1978) and guinea-pig (Carswell & Nahorski, 1983).…”