Acute and Chronic Effects of T-1032, a Novel Selective Phosphodiesterase Type 5 Inhibitor, on Monocrotaline-Induced Pulmonary Hypertension in Rats

We examined the hemodynamic property of T-1032 (methyl 2-(4-aminophenyl)-1,2-dihydro-1-oxo-7-(2-pyridylmethoxy)-4-(3,4,5-trimethoxy-phenyl)-3-isoquinoline carboxylate sulfate), a novel selective phosphodiesterase type 5 (PDE5) inhibitor, and evaluated the chronic effect of T-1032 on cardiac remodeling and its related death in monocrotaline (MCT)-induced pulmonary hypertensive rats. T-1032 (1, 10, 100 μg/kg, i.v.) significantly reduced mean arterial pressure (MAP) and right ventricular systolic pressure (RVSP) without a change in heart rate. The change in RVSP was more potent than that in MAP with 1 μg/kg T-1032 treatment (RVSP: −8.2±1.2%, mean arterial pressure: −5.7±1.2%), and reductions in RVSP and MAP reached a peak at doses of 1 and 10 μg/kg, respectively. In contrast, nitroglycerin (0.1, 1, 10 μg/kg, i.v.) and beraprost (0.1, 1 μg/kg, i.v.) did not cause a selective reduction in RVSP at any dose. When T-1032 (300 ppm in diet) was chronically administered, it delayed the death, and significantly suppressed right ventricular remodeling (T-1032-treated: 0.318±0.021 g, control: 0.401±0.013 g, p