Effect of pneumotoxicants on lactate dehydrogenase activity in airways of rats

Abstract

To assess the usefulness of monitoring changes in lactate dehydrogenase (LDH) activity in the cell-free fraction of bronchopulmonary lavage fluid as an indicator of pulmonary injury, several toxicants were administered to rats using treatment regimens which have been shown previously to result in histopathologically demonstrable pneumotoxicity. For all of the toxicants employed except exposure to 1 atm O 2, treatment did not affect recovery of lavage fluid from the lung. Lavage fluid LDH activity was elevated following treatment with paraquat, bromobenzene, and oxygen. Administration of monocrotaline using a treatment regimen which results predominantly in lung injury also produced elevated LDH activity in lavage fluid; however, treatment with this same compound using a regimen which results predominantly in hepatic injury failed to elevate lavage fluid LDH activity but resulted in a more pronounced increase in LDH activity in plasma. Similarly, the hepatotoxicant, carbon tetrachloride, produced a marked increase in plasma LDH activity without affecting that of the lavage fluid. The sensitivity of this method in detecting increased LDH activity was minimally dependent upon the volume of fluid used for lavage or on the number of successive lavages used for analysis. It appears to be useful as a rapid screening test for detecting lung injury from chemicals which are pneumotoxic following inhalation or systemic administration.