Non-hypoxaemic pulmonary oedema induced by alpha-naphthyl thiourea in the rat

The time course of the respiratory consequences of alpha-naphthyl thiourea (ANTU)-induced lung oedema was studied in adult albino rats, up to 6 h after the injection of 5 mg/kg ANTU. Control rats were injected with olive oil (ANTU solvent). After 6 h, pulmonary extravascular water increased by 50% in ANTU-treated rats and the volume of the pleural effusion reached 3.4 +/- 0.1 ml (mean +/- s.e. mean). The most striking point is the absence of hypoxaemia in the ANTU-treated rats: PaO2 = 103 +/- 1.5 Torr vs 100 +/- 1 Torr in the control rats. The non-decreased PaO2 can be related to the patency of the alveolar airspaces. The predominant location of the oedema in the lung interstitium is caused by a specific lymphatic drainage pathway towards the pleura in the rat which prevents alveolar flooding. Histological findings support this hypothesis. PaCO2 is unaltered: 32 +/- 1 Torr in ANTU rats vs 33.5 +/- 1 Torr in control rats. A slight downward shift of arterial pH is found in ANTU rats: (7.440 +/- 0.010 vs 7.475 +/- 0.010, P less than 0.01). Concomittently (HCO3-)a decreases in ANTU-treated rats (22.2 +/- 1.2 mmol l-1 vs 24.8 +/- 0.6 mmol l-1, P less than 0.01). The absence of hypoxaemia is common with normobaric oxygen (02) and ANTU-induced lung oedema in the rat. A comparison is made between 02 and ANTU toxicity, as for respiratory events and histological features.