title: The duration of the pulmonary paraquat toxicity--enhancement effect of O2 in the rat.
abstract: The duration of the pulmonary paraquat toxicity-enhancement effect of O2 has been examined in Wistar rats. In one experiment, various groups of normal animals were given a single dose (5 mg/kg body wt) of paraquat and after different periods were exposed to continuous breathing of normobaric 74% O2 in airtight chambers until dead or up to 10 days. In a reverse experiment, a large number of rats were first exposed for 6 days to continuous breathing of normobaric 74% O2 and were then separated into various groups which received a single dose of paraquat (5 mg/kg body wt) after various periods of breathing normal air, ranging from 0 to 96 hr. The extent of pulmonary damage in both experiments was evaluated by histologic examination and by biochemical determination of total collagen content of the lungs. It was found that the duration of the pulmonary damage induced by paraquat that is enhanced by continuous breathing of high O2 concentration lasts 24 to 48 hr. It was also observed that 12 to 24 hr after paraquat administration and continuous breathing of high O2 concentration pulmonary lesions are severe and extensive, and in animals surviving 6 or more days there was also incipient interstitial fibrosis. The reverse sequence of treatment (O2 + paraquat) resulted in no mortality and no pulmonary lesions. Additional controls treated with each of the pulmonary toxins alone also revealed no lung changes.
mesh_terms: D000818:Animals; D003094:Collagen / Q000032:analysis; D004357:Drug Synergism; D008168:Lung / Q000032:analysis / Q000187:drug effects* / Q000473:pathology; D008297:Male; D010100:Oxygen / Q000633:toxicity*; D010269:Paraquat / Q000633:toxicity*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D003094:Collagen; D010269:Paraquat; D010100:Oxygen