An ecto-ATPase activity present in Leishmania tropica stimulated by dextran sulfate

In this study we report the effects of sulfated polysaccharides on the ecto -ATPase activity of intact cells of Leishmania tropica. Increasing concentr ations of dextran sulfate stimulated progressively the ecto-ATPase activity , but did not modify other ecto-enzymes present on the surface of this para site, such as 5'nucleotidase, 3'nucleotidase and a membrane-bound acid phos phatase activity. This stimulation was not observed when other sulfated pol ysaccharides such as chondroitin sulfates and heparin were tested. It depen ds on size and charge of the dextran sulfated molecule. When the cells were incubated in the presence of dextran sulfate Mr 8,000; 40,000 and 500,000 the stimulation of the ecto-ATPase activity was 11%; 23%; and 63%, respecti vely, and the stimulation was not observed when desulfated dextran (Mr 40,0 00) was used. The effects of dextran sulfate also depend on pH of the mediu m. At pH 7.5, the stimulation was over 60%, whereas at pH 8.5 only 25%, The effects of dextran sulfate 500,000 on the ecto-ATPase activity was totally abolished by spermidine and partially by putrescine, two polyamines synthe sized and released by Leishmania.