Autonomic and autacoid activity in antigen‐sensitized and control ovine pulmonary vein and artery

Abstract

Spirally cut strips of ovine pulmonary vein and artery were studied in isolated organ baths and their responses to selected autacoid and autonomic agents were compared. In addition blood vessels taken from horse plasma-sensitized sheep were compared with their respective controls. Pulmonary vein and artery exhibited qualitative and quantitative differences in their autacoid and autonomic reactivity. Veins were more sensitive in responding with contractions to histamine (HIST) and carbachol (CARB) when compared with arteries. Responses of these vessels differed qualitatively to 5-Hydroxytryptamine (5HT); phenylephrine (PE) and adrenaline (ADR): arteries responded with strong contraction and veins with relaxations. Isoproterenol (ISOP) effectively relaxed veins but was either without effect or produced 10%-15% relaxations of precontracted arterial strips. Phentolamine competitively antagonized ADR and PE-induced contractile responses of arteries while on veins, ISOP and PE dose-response curves (DRCs) were shifted to the right in the presence of propranolol. Mepyramine inhibited venous and arterial responses to HIST. Comparisons between sensitized and non-sensitized sheep vasculature revealed a significant (P less than 0.05) decrease in the activity of spasmolytic agonists on veins, i.e. relaxant actions of 5HT, PE and ISOP were significantly impaired. In addition the activity of 5HT to contract pulmonary artery was significantly (P less than 0.05) increased when compared with controls. Present investigation suggests: (i) the predominance of H1-histaminergic receptors in ovine pulmonary vasculature; (ii) the preponderance of alpha and beta-adrenergic receptors in pulmonary artery and vein, respectively; (iii) that antigenic sensitization exaggerates the pathological state by causing a decrease in spasmolytic activity with a parallel increase in spasmogenic activity.

Effect of histamine on lung contractile elements in growing cattle

“…6 The results obtained in neonatal calves and young adult cattle in the study reported here are identical in qualitative terms to those obtained in sheep, 7 dogs, 8 and guinea pigs 6,9 ; however, they are strikingly different quantitatively. This finding is in contradiction of data that indicate that the pulmonary arteries react to histamine much more strongly than do pulmonary veins in rabbits 5 and humans.…”

“…1 The main bioactive substance released by mast cells during degranulation is histamine, which induces tracheobronchial spasms, pulmonary arterial vasoconstriction, and an increase in capillary permeability. Furthermore, whereas histamine clearly acts as a pulmonary arterial vasoconstrictor in rabbits 5 and humans, 6 it appears to have a venoconstricting effect in sheep, 7 dogs, 5,8 and guinea pigs. Furthermore, whereas histamine clearly acts as a pulmonary arterial vasoconstrictor in rabbits 5 and humans, 6 it appears to have a venoconstricting effect in sheep, 7 dogs, 5,8 and guinea pigs.…”

Opposing responses of the rat pulmonary artery and vein to phenylephrine and other agents in vitro

“…Differences in the distribution of adrenergic receptors and the expression of NO synthase between the pulmonary artery and veins were not explored at the molecular level. Some studies have shown that phenylephrine significantly constricts the pulmonary arteries of humans, dogs, pigs, and cattle [ 10 , 23 , 30 , 31 ]; therefore, we speculate that the effect of phenylephrine on the pulmonary vascular may have significant species differences.…”