Effects of microbial products on glucose consumption and morphology of macrophages.

We studied the effects of microbial products on glucose consumption and morphology of macrophages which were elicited with thioglycollate medium. Macromolecules such as lipopolysaccharide (LPS), tumor promoters, and respiratory inhibitors increased macrophage glucose consumption without inducing evident morphological changes. The assay system was used to screen for active substances in culture broth extracts from actinomycetes. Among them, aureothin increased glucose consumption of macrophages and inhibited respiration of a rat mitochondrial fraction. Concanamycin A induced morphological changes of macrophages into needle-like shapes but not of cloned cells including the macrophage-like cells J774.1. This compound changed fibrosarcoma L929 cells into round shapes without affecting the shape of a nontransformed fibroblast, BALB/3T3 cells. Antimycin and concanamycin A increased tumor-killing activity of macrophages when added during the effector phase. These results suggest that this assay system is simple and sufficiently reproducible and thus usable for screening for modulators of macrophage function among natural products.