NSP-805 is a potent and selective inhibitor of guinea pig cardiac phosphodiesterase 3 (PDE3), and a cardiotonic agent with vasodilator properties.
In isolated guinea pig left atria, NSP-805 shows positive inotropic EC50 value in order of potency of 0.18 μM. The in vitro positive inotropic effects of NSP-805 is accompanied by increases in tissue cyclic AMP and abolished by carbachol[1].
In anesthetized dogs, intravenous (i.v.) injection of NSP-805 produces dose-dependent increases in left ventricular VVdp/dtmax and decreases in aortic blood pressure (ABP) with relatively small increases in heart rate (HR). The ED50 value for LVdP/dtmax of NSP-805 is 12 μg/kg. When the drugs is administered intraduodenally to anesthetized dogs, the ED50 value for LVdP/dtmax of NSP-805, is approximately 10 μg/kg. In the propranolol-induced heart failure model, NSP-805 completely improves the hemodynamic state of heart failure to normal levels[1]. NSP-805(100 μg/kg) reduces systemic blood pressure significantly, but the increase of chorio-retinal blood flow is less than that at the low dose of NSP-805 (40 μg/kg) in rabbit eyes[2].
[1]. Mochizuki N, et al. Cardiovascular effects of NSP-804 and NSP-805, novel cardiotonic agents with vasodilator properties. J Cardiovasc Pharmacol. 1993 Jun;21(6):983-95. [2]. Uchida H, et al. [The effect of phosphodiesterase type 3 inhibitor on chorio-retinal blood flow in rabbits eyes]. Nippon Ganka Gakkai Zasshi. 2002 Oct;106(10):615-20.