Pharmacological studies on the pulmonary vein of the horse. I. Effects of selected spasmogens

Abstract

Horses suffer from a respiratory condition, similar to human allergic asthma, that is characterized by severe dyspnea, wheezing, coughing, and mucus production. Mediator substances released during the allergic reaction may contract airways and pulmonary vasculature. Nothing is known of the effects of autacoids and other vasoactive substances on equine pulmonary vessels. Therefore, spiral strips of equine pulmonary vein were prepared in vitro and the effects of histamine (H), 5-hydroxytryptamine (5HT), bradykinin (BK), carbachol (Carb), and phenylephrine (phen) were studied. The order of contractile effectiveness for the agonists on the vein was found to be 5HT greater than H greater than Bk greater than Phen greater than Carb, although H consistently produced the greatest maximal effects. H1-receptors appeared to mediate H contractions while H2-receptors had no measurable effect. 5HT responses were mediated directly by 'D-type' smooth muscle receptors. Bk produced contractions but of a lesser magnitude than either H or 5HT. Varying degrees of tachyphylaxis were observed for each agent. alpha-Adrenergic receptor stimulation by Phen initiated low-magnitude contractions whereas Carb exhibited virtually no activity on the pulmonary vein. Contractile responses of pulmonary veins to various spasmogens may contribute to the equine asthmatic response by raising vascular hydrostatic pressure, thereby enhancing edema formation.

5‐hydroxytryptamine Induces Relaxation of Goat Pulmonary Veins: Evidence for the Noninvolvement of M and D‐tryptamine Receptors

“…The antagonism of methysergide to 5-HT-induced contractile responses of goat pulmonary arteries demonstrates the existence of classical D receptors in this tissue. This observation is not inconsistent with similar findings in the pulmonary blood vessels of several other mammalian species (Somlyo & Somlyo, 1970;Eyre, 1971Eyre, , 1975aJoiner et al, 1975;Su & Bevan, 1976;Hanna & Eyre, 1978;Chand & Altura, 1980). 5-HT-induced relaxations of the goat pulmonary veins were not blocked by indomethacin (a potent blocker of prostaglandin (Eyre, 1975a;Feniuk et al, 1979;Chand & Altura, 1980).…”

“…5 5-HT-induced arterial contractile responses were antagonized by methysergide, showing the occurrence of classical D receptors in the goat pulmonary artery. 6 It is concluded that differential reactivity of pulmonary arteries and veins to vasoactive agents may play differential role(s) in the pathophysiology inflammatory activity in goat pulmonary veins.Recently, there has been some interest in the autonomic and autacoid pulmonary pharmacology of farm animals (Eyre, 1971; 1975,a,b;Hanna & Eyre, 1978; Chand, DeRoth & Eyre, 1979;Chand & Altura, 1980). During the course of one of these investigations, 5-hydroxytryptamine (5-HT) was found to relax goat trachea (Chand et al, 1979).…”

Equine immunology 2: Immunopharmacology — Biochemical basis of hypersensitivity

“…However, Eyre and Lewis (1973) demonstrated an increase in kinin production in horse blood during experimentally-induced anaphylactic responses. Prostaglandins and kinins are described as secondary mediators of inflammation because they are airway smooth muscle of horses (Hanna and Eyre 1978). 5-Hydroxyfrypfamine.…”

The Responses of Pulmonary and Systemic Circulation and Airway to Allergic Mediators in Anesthetized Rats

“…23) Histamine is also reported to exert pulmonary vasodilator actions preferentially during vasoconstriction and in other conditions of high PAP in animals [18][19][20] including rats. 20,24) However, our study showed no changes in PVR in response to histamine, indicating that histamine did not cause pulmonary vasoconstriction or vasodilatation in in vivo rat lungs.…”