The intact cells had been incubated with 100 M Mito-TEMPO, in the presence or absence of 2.five M of heme, as indicated on the abscissa, for 20 min. Na+/K+ ATPase activity (B) and Mobile viability (C) had been determinated. The values signify the imply common error of at the very least a few impartial experiments. Statistically substantial when in comparison to cells incubated with two.5 M of heme without having Mito-TEMPO (n = three, P < 0.05)stimulatory effect of heme on the Na+/K+ ATPase activity (Fig 11B). In this condition, MitoTEMPO did not interfered on cell viability (Fig 11C).Recent studies have demonstrated that H2O2 could play a key role in intracellular signal transduction through the reversible activation / inactivation of the active site of several enzymes [12, 14, 45, 46]. Protozoan parasites of genus Tryoanosoma are able to generate H2O2 during its growth [12]. High levels of H2O2 produced at log phase of growth of Leishmania amazonensis (Fig 1) could be indicating that this molecule is important to parasite to grow. Knowledge of signal transduction pathways in protozoan parasites is extremely important, considering that understanding the cellular physiology of these organisms can help the design of new drugs and the understanding of the interaction with its host. Felibertt et al [26] proposed in 1995 that the Na+/K+ ATPase activity could be involved in the generation of an electrochemical gradient of Na+ and K+ in L. mexicana. The Na+ gradient gives the energy required for the transport of nutrients and other solutes. A signaling pathway activated by heme involving phosphatidylinositol-specific phospholipase C (PI-PLC) and PKC, which leads the activation of Na+/ K+ ATPase, has been described in L. amazonensis [25]. Leishmania PKC-like has been associated with biological properties such as interaction with host macrophages [30,47] and maintenance of ion homeostasis [25, 27, 30]. Free heme, an amphipathic porphyrin containing iron, can catalyze the production of reactive oxygen species [6]. In this work, we show that promastigotes of L. amazonensis in the presence of 2.5 M heme17148450 have a spike in the production of H2O2, reaching an 1415834-63-7 customer reviews amount of 74 6 pmol (Fig 2). It is currently accepted that organisms have not only adapted to deal with oxidizing species but also developed mechanisms to make use of these free radicals [10]. It has been reported that ROS generated by heme activates the intestinal epithelial cells through activation of focal adhesion kinase (FAK) and the polymerization of the actin cytoskeleton [9].