Early damage indicators in the lung I. Lactate dehydrogenase activity in the airways

The rapid determination of damage in the lung is important in developing screening methods for ranking the toxicity of inhalable pollutants. The presence of lactate dehydrogenase (LDH) activity in the airways was found to be a sensitive indicator of acute toxicity to lung cells. The airway content of LDH increased after bronchopulmonary lavage of Syrian hamsters with increasing amounts of Triton X-100, with a correlation coefficient of 0.98. No increase in iron content of the lavage fluid occurred, indicating that lysed erythrocytes were not the source of the LDH. The isoenzyme pattern of the LDH activity in the lavage fluid suggested the LDH was released from lung cells. The method of detecting early lung injury by the presence of LDH in the airways can be used in one of two ways: The toxic material to be tested may be introduced into the lung by pulmonary lavage and the released LDH may be measured in the same lavage fluid; or in animals exposed to toxicants in aersol form, a lavage can be performed after exposure to obtain a sample of the LDH in the airways.