HO activities in the aortas of young (8-week-old) SHRs and age-matched WKYs.

A significantly lower HO-1 activity in SHRs than WKYs (†P < .05) was registered. Hemin (Hem) and CO greatly increased HO activity in SHRs and age-matched WKYs. ZnPP and HbO₂ nullified the hemin-dependent increase in HO activity. **P < .01 versus control (Ctrl). *P < .05 versus hemin-treated animals. Nitrogen (N₂), biliverdin (Bil), and iron (Fe) had no effect on HO activity. n = 4 for each group. Error bars indicate means ± SEM.