Acta Tropica 66 (1997) 109–118 Detrimental effect of nitric oxide on Trypanosoma cruzi and Leishmania major like cells S.C. Bourguignon a,b , C.R. Alves a,b , S. Giovanni-De-Simone a, * a Laborato ´rio de Microsequ ¨enciamento de Proteinas, Departamento de Bioquı ´mica e Biologia Molecular, Instituto Oswaldo Cruz, Fiocruz, A. Brasil 4365, 21 045 – 900, Rio de Janeiro, Brasil b Departamento de Biologia Celular e Molecular, Instituto de Biologia, Uniersidade Federal Fluminense, Nitero ´i 24 210, Rio de Janeiro, Brasil Received 2 August 1996; received in revised form 8 November 1996; accepted 7 March 1997 Abstract The production of nitric oxide (NO) by activated macrophages has been reported to be a non-specific immune-effect mechanism against several parasites. In this work we investigate whether the NO has a detrimental effect on the intracellular parasites of the genus Leishmania and as well as Trypanosoma cruzi. This was assessed by co-cultivating infective Leishmania promastigotes and T. cruzi trypomastigotes and non-infective T. cruzi epimastig- otes forms of the parasites in the presence of the NO releasing molecule, S-nitroso-N-acetyl- DL-penicillamine (SNAP). We demonstrate that the NO has the ability to inhibits the growth of all parasites in a concentration dependent manner. In addition, by analysing purified protein and cell homogenates of L. major (promastigotes) and T. cruzi (epimastigotes and trypomastigotes) we demonstrated that the NO may regulate the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity of both parasites. © 1997 Elsevier Science B.V. Keywords: Trypanosoma cruzi ; Leishmania major ; Nitric oxide; Glyceraldehyde-phosphate- dehydrogenase * Corresponding author: Telefax: +55 21 5903495; e-mail: dsimone@gene.dbbm.fiocruz.br 0001-706X/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S0001-706X(97)00033-8