Human chorionic gonadotropin induces nitric oxide synthase mRNA in mouse peritoneal macrophages

We examined the effects of human chorionic gonadotropin (hCG) on the production of nitric oxide (NO) by mouse peritoneal macrophages. hCG had no effect on NO synthesis by itself, whereas recombinant interferon-gamma (rIFN-gamma) alone had modest activity. When hCG was used in combination with rIFN-gamma, there was a marked cooperative induction of NO synthesis in a dose-dependent manner. The optimal effect of hCG on NO synthesis was shown at 6 h after treatment with rIFN-gamma. This increase in NO synthesis was reflected as increased amount of inducible NO synthase (iNOS) mRNA. NG-monomethyl-L-arginine, and arginase inhibited rIFN-gamma-plus-hCG-induced NO production. On the basis of these observations, we conclude that hCG activates expression of iNOS mRNA in mouse peritoneal macrophages accompanied by NO accumulation via pathway dependent on L-arginine in the culture medium.