[The role of L-arginine and L-citrulline in activated macrophage against Toxoplasma gondii infection in vitro].
OBJECTIVE
To determine whether both the production of NO and the toxoplasmastatic or toxoplasmacidal activity of activated macrophages cultured in physiologic levels of arginine can be enhanced by increasing the availability of arginine, or citrulline.


METHODS
After the activated M phi were infected with the RH strain of T. gondii, the levels of NO production, the infection rate of M phi and the number of tachyzoites in parasitophorous vacuoles were determined after the M phi were cultured in medium added with various concentrations of L-arginine or L-citrulline for 18 h.


RESULTS
(1) The multiplication of intracellular toxoplasmic tachyzoites could be inhibited by activated macrophages, depending on the production of NO in the presence of physiologic levels of arginine. (2) Increased exogenous arginine or citrulline resulted in a significant elevation of NO production induced by activated macrophages and further reduction of infection rate of macrophages as well as inhibition of multiplication of intracellular tachyzoites. (3) Citrulline could fully substitute for arginine in enhancing NO production and toxoplasmastatic or toxopasmacidal activity.


CONCLUSIONS
The physiological levels of arginine were able to induce sufficient intrinsic NO production to inhibit intracellular multiplication of toxoplasmatic tachyzoite but unable to protect cell from infection and that increasing the substrate levels for NO biosynthesis may enhance in vitro toxoplasmastatic or toxoplasmacidal activity of activated macrophages.
Zheng
C
C
Department of Parasitology, Fujian Medical University, Fuzhou 350004.
Lin
J
J
D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D002478:Cells, Cultured; D002956:Citrulline / Q000494:pharmacology*; D005260:Female; D008262:Macrophage Activation / Q000187:drug effects*; D017737:Macrophages, Peritoneal / Q000378:metabolism / Q000469:parasitology*; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis; D014122:Toxoplasma
D002956:Citrulline; D009569:Nitric Oxide; D001120:Arginine