Lactate dehydrogenase isoenzymes in hamster lung lavage fluid after lung injury

Lactate dehydrogenase (LD) levels and isoenzyme patterns were determined in the cell-free supernatant fractions of lung lavage fluid from hamsters exposed to alpha-quartz, iron oxide, Triton X-100, 100% O₂, or 200 ppm SO₂. The isoenzyme patterns were compared to those derived from hamster lung homogenates, serum, polymorphonuclear neutrophils (PMNs), pulmonary macrophages, and red blood cells. The isoenzyme patterns from alpha-quartz- and iron oxide-exposed animals resembled each other and were similar to that of PMNs. In contrast, the pattern seen after Triton X-100 exposure was similar to those of whole lung homogenates and of red blood cells. A 96-hr exposure to 100% O₂ yielded an LD isoenzyme pattern in lung lavage fluid similar to that of serum. Exposure to SO₂ did not alter LD levels, showing that upper airways damage is not reflected by changes in LD in lung lavage fluid. We conclude that LD isoenzyme patterns of lung lavage fluid can be used to differentiate among types of pulmonary injury and may help identify the sites of injury.