Indole-acetic acid, 3-methyl indole and type 2 pneumonocyte hyperplasia in a proliferative alveolitis of cattle
Pirie, H.M.; Breeze, R.G.; Selman, I.E.; Wiseman, A.
Veterinary Record 98(13): 259-260
1976
ISSN/ISBN: 0042-4900 PMID: 1265993 Document Number: 105584
To investigate the aetiology of fog fever, groups A and B (each containing four one-year-old beef calves) received a single i/v infusion of 3-methyl indole (3MI) or indole-acetic acid (IAA). The dose was 0.07 g/kg as 0.11 g/ml solutions in propane 1,2 diol over a 12-hour period. Calves were slaughtered 96 hours after commencement of infusion. Group B and C (controls) showed mild pulmonary eosinophilia, and globule leucocytes were found in the tracheobronchial epithelium. Group A developed alveolar epithelial hyperplasia, which was multifocal in two calves and diffuse in two. Electron microscopy showed proliferation of type 2 pneumonocytes. There was also interstitial emphysema, pulmonary oedema, congestion and eosinophilia, focal formation of hyaline membranes, proliferation of terminal bronchiolar epithelial cells and appearance of globule leucocytes in the tracheobronchial epithelium. Reports suggest that 3MI may disrupt cell membranes of the alveolar wall and interfere with production of surfactant by type 2 pneumonocytes. Although oral administration of 3MI, IAA or L-tryptophan produces lesions typical of fog fever, it is not clear whether the presence of these substances in grass can account for the outbreaks of disease when cattle are moved from poor to better pasture in the autumn.