EFFECT OF EBSELEN ON BOVINE AND RAT NITRIC-OXIDE SYNTHASE ACTIVITY ISMODIFIED BY THIOLS

The inhibition of nitric oxide synthase (NOS) by ebselen, 2-phenyl-1,2 -benzisoselenazole-3(2H)-one, was reversed by the addition of 10(-5) M dithiothreitol, suggesting that ebselen reacts with a critical thiol group of NOS in the inhibitory mechanism. In the presence of 10(-4) to 10(-3)M dithiothreitol, ebselen dose-dependently enhanced NOS activit y, implicating another interaction of ebselen with NOS under these con ditions. Thus, the effect of ebselen on the NOS activity is modified b y thiols.