The digestion of bacterial macromolecules by phagocytic cells: the effect of mepacrine and ethanol.

The digestion of radiolabelled DNA, RNA and protein from two species of bacteria was measured after their ingestion by neutrophils and monocytes. The Escherichia coli (W3110T-) strain was more susceptible to digestion than Staphylococcus aureus. Monocytes solubilized the majority of bacterial DNA to trichloroacetic acid (TCA)-soluble oligonucleotides, which were released rapidly from the cell, whereas neutrophils digested little DNA and retained most as a high molecular weight residue. Both monocytes and neutrophils released about 30% of DNA as large TCA-insoluble fragments. However, neutrophils were more proficient than monocytes at degrading bacterial RNA. Monocytes and neutrophils digested bacterial protein equally well. The drug mepacrine hydrochloride inhibited phagocytosis of bacteria by both neutrophils and monocytes, although monocytes were more sensitive to the drug. Mepacrine specifically inhibited the terminal digestion of DNA by monocytes to TCA-soluble molecules, whereas digestion to large molecular weight fragments apparently was not affected. Ethanol also inhibited the breakdown of DNA by phagocytic cells.