Olfactory and hepatic changes following a single inhalation exposure of 3-trifluoromethyl pyridine in rats: concentration and temporal aspects.

The effects of a single exposure to 3-trifluoromethyl pyridine (3FMP), were investigated in two studies. In the first study, rats were exposed nose only to 0, 50 or 800 ppm 3FMP for periods of 15 min to 4 h. Half were sacrificed on day 3 and the remainder on day 10. In the second study, rats were exposed whole body to 0, 0.1, 1.0, 10 or 50 ppm 3FMP for 6 h, with sacrifices immediately after exposure (6 h), 24 h and on days 3 (48 h after exposure started) 5, 8, 11, 35, 70 and 157. Effects were seen in the olfactory epithelium at concentrations of 1 ppm and above and in the liver at concentrations of 50 ppm and above. In the olfactory epithelium the earliest changes were seen immediately after exposure and by 24 h this progressed to extensive necrosis with sloughing of the epithelium. By day 3, the epithelium was replaced by undifferentiated basophilic cells, considered to reflect early regeneration. Regeneration progressed to complete recovery between days 70 and 157, no changes were seen in the nasal respiratory epithelium, an olfactory function test on rats exposed for 6 h to 50 or 10 ppm 3FMP showed a reduced sense of olfaction at days 3 and 5 with complete recovery on subsequent days, indicating functional recovery in advance of histological normality. Single cell necrosis was seen in the liver at day 3 after 30 min exposure and immediately after 6 h exposure to 50 ppm 3FMP. At 24 h after a 6 h exposure to 50 ppm this had progressed to necrosis, haemorrhage and moderate cytoplasmic hepatocyte vacuolation in centrilobular areas. The lesion had completely recovered by day 5.