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Abstract
Phenazine methosulfate, a cationic electron carrier, inhibits the extracellular growth
of promastigotes and the conversion of amastigotes into promastigote forms of Leishmania
mexicana amazonensis. Growth inhibition and damage of extracellular parasites by PMS
was counteracted by superoxide dismutase, a scavenger of the superoxide anion (O2-),
and to a lesser extent, by catalase, a scavenger of hydrogen peroxide (H2O2). Inactivated
dismutase and catalase were ineffective. Thus, damage of isolated L.m. amazonensis
by phenazine methosulfate, involves the participation of O2- and H2O2. The role of
the oxygen metabolites in the toxicity of phenazine methosulfate remains unknown.
That O2- can damage the parasites is supported by the finding that superoxide dismutase
also protected promastigotes from damage induced by oxygen intermediates generated
by a xanthine-xanthine oxidase system. Killing of the parasites by crystal violet,
a triphenylmethane, or basic blue 24, a phenothiazine, was not inhibited by superoxide
dismutase.