SCHISTOSOMA-MANSONI CERCARIAE - STIMULATION OF ACETABULAR GLAND SECRETION IS ADAPTED TO THE CHEMICAL-COMPOSITION OF MAMMALIAN SKIN

The chemical signals of mammalian skin that stimulate the secretion of acetabular gland contents of Schistosoma mansoni cercariae were deter mined by exposing cercariae to fractions of human and pig skin surface obtained by thin-layer chromatography. Postacetabular gland secretion was stimulated by hydrophilic skin extracts but was often combined wi th a secretion of preacetabular glands. Secretion of preacetabular gla nds, which contain enzymes for skin lysis, could be selectively stimul ated with skin surface lipids. Two different mechanisms of lipid-stimu lated preacetabular gland release could be distinguished. First, secre tion in combination with penetration behavior and probably tegument tr ansformation was stimulated by the fraction of free fatty acids. Secon d, secretion independent of penetration behavior and tegument transfor mation was exclusively stimulated by glucosylceramides and phospholipi ds, probably phosphatidylcholines. The secretion mechanisms seem to al low a continuous lysis of epidermal macromolecules during the skin pas sage of the cercariae. Free fatty acids occur in the uppermost skin la yers and may stimulate the combination of the first response; phosphol ipids and glucosylceramides are restricted to deeper epidermal layers and may stimulate the enzyme secretion there. An active preacetabular gland release was also stimulated by toxic chemicals, which could sugg est an emergency penetration program for impaired cercariae.