ANAPHYLACTIC CONTRACTION OF PULMONARY BLOOD VESSELS OF CHICKEN

Abstract

1 Isolated pulmonary arterial and vein strips from sensitized or non-sensitized chickens exhibited dose-dependent contractions to adrenaline>, noradrenaline>, 5-hydroxytryptamine>, histamine>, dopamine. Individual variability in the responsiveness of the vessels to agonists was marked. In general veins were 2 to 25 times more sensitive to agonists than arterial strips. 2 Isoprenaline (a relatively specific β-adrenoceptor agonist) induced relaxations of the submaximally contracted pulmonary vein and arteries at low doses and contractions at high concentrations. 3 Contractile responses to acetylcholine or carbachol were not regularly recorded; only 50% of the vessels reacted to cholinoceptor agonists over a wide threshold dose range. 4 Chicken pulmonary vessels were found relatively insensitive to bradykinin. 5 Effects of prostaglandins were variable. Prostaglandin induced dose-related contractions of the vein and arterial strips; prostaglandins E₁ and E₂ at low doses relaxed partially contracted pulmonary artery irrespective of the spasmogen used and further increase in doses induced either no effect or contractions. Prostaglandin E₁ induced marked and rapid contractions of the vein. Prostaglandin E₂ induced relaxations of the prostaglandin F_2α-contracted vein only, but produced no effect or slight contractions of the veins partially contracted to other spasmogens. 6 Pulmonary arterial and vein strips obtained from chickens sensitized to horse plasma exhibited Schultz-Dale contractions of variable magnitude and duration to specific antigenic challenge only. In many vessels, antigen-induced contractions were associated with marked increase in spontaneous activity. 7 The importance of the Schultz-Dale reaction in avian pulmonary vessels is discussed in relation to the right heart dilatation associated with anaphylaxis in the chicken.