Pulmonary oedema induced by ANTU, or by high or low oxygen concentrations in rat--an electron microscopic study.

Pulmonary oedema has been experimentally induced in rats using either an intraperitoneal injection of alpha-naphthyl thiourea (ANTU) or by variation of atmospheric oxygen content. For the first time an electron microscopic study of the development of ANTU-induced lung oedema has been made. At 2 hours blebbing and scalloping of endothelial cells and interstitial oedema were observed, each showing increasing severity with increase of dose—3, 10 and 50 mg/kg doses. By 6 hours, in the 50 mg/kg treated animals, epithelial damage was also apparent. No alteration in mean alveolar size or in the distribution of alveolar lining cells was found. The breathing rate of the rats was slowed for the first 3 hours and then increased well above normal levels. Hyperoxic conditions (99-100% O2 at 1 atm/pressure) produced interstitial oedema by 6 hours, followed at 24 hours by both endothelial and epithelial damage. Hypoxic conditions (7-10% O2 at 1 atm/pressure) did not produce these effects. Both hyperoxic and hypoxic conditions were associated with a significant increase in the mean alveolar size, an apparent decrease in number of Type III pneumonocytes and in the macrophages when related to alveolar cell number, while the counts of Types I and II pneumonocytes remained within the normal range.