Covalent binding of [14C]thiourea to protein in lungs from endotoxin-treated rats.

Administration of thiourea to mature male rats at a dosage of 3.5 mg/kg (ip) produced marked pleural effusion by 2 hr (3-4 ml). Pretreatment with bacterial lipopolysaccharide (endotoxin) significantly reduced this pleural effusion (less than 0.5 ml). Despite this unequivocal effect, there was no corresponding reduction in the covalent binding of [14C]thiourea to lung protein. These data indicate that the protective effect of endotoxin against the initial stages of thiourea pneumotoxicity does not involve a reduction in binding of the [14C]thiourea or a metabolite to lung protein. However, alterations in low levels of binding to specific cell types or particular protein(s) relative to covalent binding cannot be ruled out.