The effect of high temperature on alveolar macrophage counts in bronchoalveolar lavage fluid of F344 rats.

To determine the effects of high temperature on the number of alveolar macrophages (AMs) in bronchoalveolar lavage (BAL) fluid in rats, F344 rats were housed in environment chambers at 23 degrees C, 30 degrees C or 35 degrees C for up to 14 days. The number of AMs in the BAL fluid was significantly decreased in rats housed at 35 degrees C on days 7 and 14, compared to the control group housed at 23 degrees C. The total protein content and lactate dehydrogenase activity did not change at high temperatures in BAL supernatant, indicating that there was no increase in alveolar/capillary barrier permeability or lung cellular injury. The results might suggest that high temperature (35 degrees C) affects the pulmonary defense mechanism.