Lysosomal enzyme activity in pulmonary alveolar macrophages from conventional, germfree, monoassociated, and conventionalized rats.

Pulmonary alveolar macrophages (PAM) were harvested from conventional (CONV), germfree (GF), conventionalized, and monoassociated (MA) rats. Germfree rats had significantly fewer PAM than did their CONV, conventionalized or MA counterparts. The bronchopulmonary wash from the CONV and conventionalized rats contained higher lysosomal specific activity for beta-glucuronidase and cathepsin D than did similar washes from GF rats. Cellular and subcellular PAM fractions from GF rats also showed decreased enzyme activity in comparison with similar fractions from the PAM or CONV rats. Colonization of GF rats with one (MA) or more bacterial species (conventionalized) increased the beta-glucuronidase and cathepsin D activity of their PAM as well as total PAM. These data suggest that the intestinal flora not only enhances PAM proliferation but also is associated with an increase in their lysosomal enzyme activity.