Figure 2

Activation of rat brain HO-2 by menadione, and lack of activation by dimethoxymenadione (DMD) and pentafluromenadione (5 F-MD). HO-1 and HO-2 activity were measured as described in Methods using spleen and brain microsomes, respectively. The abscissa shows drug concentration and the ordinate shows HO activity as a percent of control in the absence of added drug. Open circles show menadione activation of HO-2, and solid triangles show lack of activation of rat spleen HO-1. Solid circles show lack of activation of HO-2 by dimethoxy analog of menadione. Open triangles show lack of activation of HO-2 by the fluoro analog of menadione.