Ang II-induced hypertension was associated with an increased constriction of the isolated thoracic aortic rings (55% from Cyp1b1+/+ vehicle-treated group) (Fig. 1a) to maximal concentration of phenylephrine (PE) and (83% from Cyp1b1+/+ vehicle-treated group) to maximal concentration of endothelin-1 (ET-1); these increases were attenuated by Cyp1b1 gene disruption (24% for PE, 52% for ET-1 compared to Cyp1b1+/+ vehicle-treated group), or castrated Cyp1b1+/+ and Cyp1b1−/− mice (20% for PE and 21% and 16% for ET-1 compared to castrated Cyp1b1+/+ vehicle-treated group) (Fig. 1a, b). Here, CYP1B1 is linked to hypertensive disorder.