The in vitro effects of various lysosomotropic agents on the gut of Schistosoma mansoni schistosomula.

Cultured Schistosoma mansoni schistosomula of various ages were exposed to several lysosomotropic agents. Weak bases such as chloroquine, ammonium chloride, and acridine orange caused gut swelling upon protonation. The latter compound fluoresced a bright orange indicating the acidic nature of the gut contents. Hydrolysis of ingested L-amino acid methyl esters also resulted in gut swelling, indicating the nonpermeant nature of the resulting L-amino acids. Neither age nor feeding status influenced these swelling effects. Treatment of schistosomula with D-amino acid esters, free L-amino acids, or methanol had no effect. Thin-layer chromatographic analysis of worms treated with radiolabeled L-leucine methyl ester provided evidence that the ester was hydrolyzed. These results support the premise that the schistosome gut is an acidic compartment and is reminiscent of a secondary lysosome in its reaction to lysosomotropic agents.