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 micro g/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 micro g/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 micro g/kg, respectively. In contrast, nitroglycerin (0.1, 1, 10 micro g/kg, i.v.) and beraprost (0.1, 1 micro g/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<0.05). Our present results suggest that T-1032 selectively reduces RVSP, and resulting in the suppression of right ventricular remodeling with a delay of the death in MCT-induced pulmonary hypertensive rats.