Leishmania mexicana: drug sensitivities of promastigotes and transforming amastigotes.

A comparison has been made of the effects of a range of antiprotozoal drugs and other metabolic inhibitors upon growing promastigotes and transforming amastigotes of Leishmania mexicana mexicana. Amastigotes transforming to promastigotes in vitro were highly susceptible to 2-mercaptoacetate, 4-pentenoate, alpha-difluoromethylornithine, ethidium bromide, acridine orange, pentamidine isethionate, allopurinol, amphotericin B, menoctone and pentostam. Promastigotes were in most cases less sensitive to these inhibitors. The results reiterate that the biochemical differences between the two developmental forms are reflected in their sensitivities to inhibitors. The transformation in vitro of Leishmania amastigotes to promastigotes may be a useful model for use as a primary screen for antileishmanial agents.