Comparative study of bronchoalveolar lavage fluid: effect of species, age, and method of lavage

The analysis of bronchoalveolar lavage fluid has been used as a probe to detect lung injury in toxicological studies and to diagnose the disease state of the lung in humans. To determine how variable the content of lavage fluid from different species is, bronchoalveolar lavage fluids from normal individuals of four species (hamster, rat, guinea pig, and rabbit) were compared for enzymatic and cellular content as well as total protein and sialic acid. In addition, lavage fluid from young adult rats and hamsters was compared to that from older animals. Finally, the effect of the method of lavage on lavage fluid content was evaluated by comparing lavage fluid obtained from an excised lung with that from a lavage performed in vivo. In general, lavage fluids from the four species were similar. However, lavage fluid from guinea pigs had higher numbers of granulocytes and higher mean beta-glucuronidase activities than fluids from other species. Rats had higher mean alkaline phosphatase activities, reflecting higher serum values of this enzyme. Older hamsters had more protein in their lavage fluid than younger animals, and older rats had lower elastase inhibitory activity than young rats. Performing lavage in vivo, as compared to in vitro, did not greatly alter the lavage fluid except for a trend toward a higher level of sialic acid in fluid taken from the living animal.