Acute bovine pulmonary emphysema

Role of metabolism in the immediate effects and pneumotoxicity of 3-methylindole in goats

Rapid infusion of 3-methylindole (3-MI) dissolved in 10% Cremophor EL in water was immediately followed by pulmonary arterial hypertension, systemic arterial hypotension, decreased minute volume and periods of apnoea in goats. Rapid intravenous infusion of Cremophor EL/water alone caused similar immediate effects to those of Cremophor EL plus 3-MI in various dosages. Pretreatment of goats with piperonyl butoxide or phenobarbitone did not significantly alter these immediate cardiopulmonary responses. But pretreatment with piperonyl butoxide prevented clinical signs and pulmonary lesions of 3-MI toxicity, whereas phenobarbitone pretreatment shortened survival time and enhanced pulmonary pathology. Cremophor EL and 3-MI dissolved in Cremophor EL caused severe in vitro haemolysis of caprine and bovine erythrocytes. There was no relationship between the immediate effects of 3-MI and the subsequent development of 3-MI-induced pneumotoxicity and deaths in control goats or in goats pretreated with piperonyl butoxide or phenobarbitone. Induction or inhibition of mixed function oxidase activity had no influence on immediate responses to 3-MI but did change the severity of clinical and pathological responses. It is concluded that there is no apparent relationship between the immediate and the pneumotoxic effects of 3-MI. It is possible that the immediate effects are the result of intravascular haemolysis.

Atypical tryptamine receptors in sheep pulmonary vein

Both the pulmonary artery and vein of the sheep contracted dose-dependently to histamine, carbamoylcholine, prostaglandin F2a, noradrenaline and bradykinin and relaxed in the presence of isoprenaline or prostaglandin E1. 2 The effect of 5-hydroxytryptamine (5-HT) on the artery was consistently to produce dose-dependent contractions without tachyphylaxis. The effect on the vein was biphasic. 5HT 5 X 10(-10) to 5 X 10(-8) M relaxed the partially constricted vein. 5-HT 10(-7) to 10(-6) m caused brief venoconstriction followed by relaxation. 5-HT greater than 10(-6) M caused dose-related contraction of the vein. 3 Methysergide effectively blocked the contractile response of the artery to 5-HT, but only weakly inhibited the contractions of the vein (dose-ratio less than 20). 4 Each of ten antagonists tested failed to inhibit the 5-HT-induced relaxation of the vein. Sheep pulmonary vein possesses tryptamine receptors which mediate relaxation and which are not of the classicl M- or D-type. These receptors appear not to be involved directly or indirectly with responses to acetylcholine, catecholamines, histamine or prostaglandins.

Comparison of naturally occurring and tryptophan-induced bovine atypical interstitial pneumonia

Pulmonary changes in field cases of bovine atypical interstitial pneumonia from Saskatchewan and Alberta were reviewed and compared with those in cattle with the same condition caused by either tryptophan or 3-methylindole. The experimentally produced changes were characterized by diffuse proliferation of alveolar pneumocytes. Similar lesions occurred in 48 field cases in animals with a history of a change in pasture or diet, whereas 107 other animals had focal exudative alveolitis, comparable to a hypersensitivity reaction. The two groups of cases are referred to as ‘dietary’ and ‘hypersensitivity atypical interstitial pneumonia', respectively. The dietary type occurred most commonly from September to November in animals 2 years and older. The hypersensitivity type occurred in younger animals throughout the year, with a peak incidence in January.