Effects of non-ionic surfactants that modify experimental tuberculosis on lipase activity of macrophages

1. Six series of non-ionic surface active polyethylene glycol ethers, whose effects on experimental tuberculosis have previously been correlated with their polyoxyethylene chain lengths, were examined for their influence on the activity of a lipase present in homogenates of normal mouse peritoneal macrophages. The surfactants are concentrated in the lysosomes of macrophages-a cell type in which the host-parasite confrontation takes place. A preparation of soy bean oil was used as triglyceride substrate; and hydrolysis at pH 4.5 was compared in the presence and absence of surfactant, the products of hydrolysis being assayed by photodensitometry of thin-layer chromatograms.2. The compounds with short polyoxyethylene chains inhibited the release of fatty acid, compared with surfactant-free standard, more than did those with long chains; and some of the latter showed actual enhancement of release. Accumulation of monoglyceride was observed in the presence of six of the seven long-chained compounds, but with none of the seven short-chained compounds.3. The similarity between this correlation of chain length of the surfactants with their effect on macrophage lipase activity, and the known correlation of their chain length with their effect on experimental tuberculosis, suggests a possible connection. How this connection might relate to the mechanism of the varying effects on tuberculosis is briefly discussed.