Improvement of mortality by long-term E4010 treatment in monocrotaline-induced pulmonary hypertensive rats.

We investigated the effects of long-term treatment with a selective phosphodiesterase 5 inhibitor E4010, 4-(3-chloro-4methoxybenzyl)amino-1-(4-hydroxypiperidino)-6-phth alazin ecarbonitrile monohydrochloride, on the survival rate of rats with pulmonary hypertension induced by monocrotaline (MCT). After an s.c. injection of 40 mg/kg MCT (day 0), male Wistar rats of 4 weeks of age were divided into four groups. Vehicle-treated rats (control, n = 8) and MCT-treated rats (n = 32) were fed a commercial diet. E4010-treated rats were given a commercial diet containing 0.01% (E4010 0.01%, n = 32) and 0.1% (E4010 0.1%, n = 32) of E4010, respectively. At day 23, all rats in the control group and 28.1% of those in the MCT group (P <.01 versus control) were alive. Although the survival rate of E4010 0.01%-treated rats was not improved (50%) compared with MCT, those at 0.1% showed a significant difference (84. 4%, P <.01 versus MCT). For MCT rats (n = 9), right ventricle weight and the levels of plasma atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), cGMP, and cyclic AMP were higher compared with control (n = 8). In E4010 0.1%-treated rats (n = 27), the right ventricular hypertrophy was suppressed, and the increase in plasma cGMP level was amplified compared with MCT without any effects on plasma ANP, BNP, and cyclic AMP levels. Accordingly, we consider that the mechanism of action of E4010 may be related to the decreased pulmonary arterial pressure caused by the augmentation of pulmonary arterial relaxation through an ANP and/or BNP-cGMP system. These results suggest that E4010 will be useful for the treatment of pulmonary hypertension.