CD-832, a new dihydropyridine derivative with both nitrate-like and Ca2+ channel antagonist vasodilator activities

Current trends in QSAR on NO donors and inhibitors of nitric oxide synthase (NOS)*

This article evaluates the quantitative structure-activity relationships (QSAR) of nitric oxide (NO) radical donors and nitric oxide synthases (NOS) inhibitors, using the C-QSAR program of Biobyte. Furoxans, triazines, amidoximes, tetrazoles, imidazoles and N(omega)-2-nitroarylamino acid analogues were included in this survey. In nine out of seventeen cases, the clog P plays a significant part in the QSAR of the NO radical donors and of the NOS inhibition. Many of the compounds must be interacting with a hydrophobic space in a non-specific way. In some cases molecular refractivity CMR/MR as well as sterimol parameters (B(1) and L) are important. Electronic effects, with the exception of the Hammett's constant sigma and the Swain-Lupton parameter F, are not found to govern the biological activity. Stereochemical and electronic features are also found to be important. Indicator variables were used after the best model was found to account for the usual structural features.

Effects of CD-832, a new calcium antagonist, on intracranial pressure in anesthetized dogs

Effects of a new calcium antagonist, CD-832, on intracranial pressure (ICP), vertebral blood flow (VBF) and common carotid blood flow (CCBF) were investigated in dogs and the results were compared with findings for nifedipine and diltiaem. Dogs were anesthetized with sodium pentobarbital and a 20-gauge needle was inserted into the cisterna magna for ICP determination. Mean arterial blood pressure (MBP), heart rate (HR), CP, VBF and CCBF were measured before and during the continuous intravenous infusion of CD-832 (0.3, 1 and 3 microg/kg/min), nifedipine (0.1, 0.3 and 1 microg/kg/min) or diltiazem (1, 3 and 10 microg/kg/min). Although the three drugs caused a comparable hypotension, differences were evident in effects of these agents on ICP, VBF and CCBF. Nifedipine and diltiazem but not CD-832 significantly increased ICP, VBF and CCBF. These results suggest that CD-832 is a unique calcium antagonist which does not increase ICP during hypotension. Because the most evident side effects of calcium antagonists are caused by vasodilation and include headache and flushing, CD-832 may possibly be useful to treat subjects with hypertension or angina pectoris.

Possible involvement of nitric oxide-cGMP pathway in the negative chronotropic effect of CD-832, a novel dihydropyridine derivative

Effects of zaprinast, an inhibitor of guanosine 3', 5'-cyclic monophosphate (cGMP)-specific phosphodiesterase, and methylene blue, an inhibitor of soluble guanylate cyclase, on the negative chronotropic response to CD-832, a novel dihydropyridine derivative with a nitrate moiety, and nifedipine were examined with isolated guinea-pig right atria in the presence and absence of isoproterenol. CD-832 and nifedipine produced concentration-dependent negative chronotropic effects both in the absence and presence of isoproterenol. In the absence of isoproterenol, the concentration-response curves for CD-832 and nifedipine were neither potentiated by zaprinast nor inhibited by methylene blue. In the presence of isoproterenol (10[-8] M), zaprinast produced a three-fold leftward shift of the concentration-response curve for CD-832, while methylene blue produced a three-fold rightward shift. The concentration-response curve for nifedipine was not affected by these agents. SIN-1, a nitric oxide (NO) donor, had no chronotropic effect in the absence of isoproterenol, but had a concentration-dependent negative chronotropic effect in the presence of isoproterenol: the beating rate decreased to values close to that in the absence of isoproterenol. These findings suggest that NO-cGMP mediated pathway is involved in the negative chronotropic actions of CD-832 under beta-adrenergic stimulation.

In-vitro negative chronotropic and inotropic effects of a novel dihydropyridine derivative, CD-832, in the guinea-pig: comparison with calcium-channel antagonists

The effects of CD-832 (4R-(-)-2-(nicotinoylamino)ethyl-3-nitroxypropyl-1,4-dihydro -2,6-dimethyl-4,3-nitrophenyl, 3,5-pyridine dicarboxylate) , a novel dihydropyridine derivative, on guinea-pig isolated myocardial preparations have been compared with those of Ca2+-channel antagonists. All ten compounds induced concentration-dependent negative chronotropic effects on preparations of isolated right atria and negative inotropic effects on isolated right ventricular papillary muscles. The order of potency for the negative chronotropic effect was CD-832 > nicardipine = gallopamil > clentiazem > nifedipine = efonidipine > amlodipine = semotiadil > verapamil > diltiazem; that for the negative inotropic effect was nicardipine = gallopamil > nifedipine > verapamil > CD-832 > diltiazem > clentiazem > efonidipine = semotiadil > amlodipine. The ratio of the EC50 (the concentration of Ca2+ antagonist having 50% of the maximum effect) for the negative inotropic effect divided by the EC50 for the negative chronotropic effect, considered to be an index of selectivity for negative chronotropic effect, was higher for CD-832, amlodipine, efonidipine and semotiadil than for the other Ca2+ antagonists. The ratio for CD-832, nifedipine, nicardipine, efonidipine, amlodipine, verapamil, gallopamil, diltiazem, clentiazem and semotiadil was 11.4, 0.29, 0.87, 35.4, 37.1, 0.65, 0.87, 0.92, 7.11 and 30.0, respectively. These findings indicate that CD-832 and the newly developed Ca2+ antagonists including amlodipine, efonidipine, semotiadil and clentiazem were selective for a negative chronotropic effect rather than for a negative inotropic effect. This 'chrono-selective' effect of these drugs might be of benefit in the treatment of cardiovascular disorders.

Vasodilation profile of CD-832, a novel dihydropyridine derivative in rabbit aorta

1. CD-832, nifedipine and nitrendipine, but not nitroglycerin and nicorandil, inhibited the KCl-induced contraction of rabbit aortas. 2. CD-832, nitroglycerin and nicorandil, but not nifedipine and nitrendipine, inhibited the norepinephrine-induced contraction of aortas. The inhibitory effects of these agents were either potentiated or inhibited by zaprinast or methylene blue, respectively. 3. On the KCl-induced contraction, the duration of CD-832-induced vasodilation was longer than that of nifedipine. Concerning the norepinephrine-induced contraction, the duration of CD-832-induced vasodilation was longer than that of nicorandil. 4. These results suggest that the mechanism of CD-832-induced vasodilation concerns both Ca(2+)-antagonistic action and a nitratelike action. Furthermore, the vasodilation is long lasting.

Organic nitrates. II. Synthesis and biological activities of 4-nitrooxymethylphenyl-1,4-dihydropyridines

Both 2-nitrooxymethyl-4-phenyl- (2) and 4-nitrooxymethylphenyl-1,4-dihydropyridines (3) represent new combinations of two different vasodilating structures. 2 could not be isolated due to its spontaneous lactonization. Derivatives of 3 were obtained via Hantzsch synthesis using nitrooxymethylated benzaldehydes. The inotropic potency in isolated porcine trabecular muscles and the vasodilator activity in isolated porcine coronary arteries of four nitrooxyphenyl-dihydropyridines were determined. Nitrendipine (NTD) and glyceryl trinitrate (GTN) were used for reference. 3 were negative inotropic, however, less than NTD and--except for the dicyano derivative 3d--more than GTN. Vasodilator properties were less pronounced than that of both nitrendipine and GTN. Vascular selectivity was low.

Protective effects of CD-832 on organ damage in stroke-prone spontaneously hypertensive rats

Effects of a newly developed Ca2+ channel antagonist, (4R)-(-)-2-(nicotinoylamino)ethyl 3 nitrooxypropyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl) 3,5-pyridine-dicarboxylate (CD-832), on hypertensive complications in stroke-prone spontaneously hypertensive rats (SHRSPs) were compared with effects of diltiazem. We examined changes in histological and hematological parameters in SHRSPs given the following treatments at 8 to 20 weeks of age: (a) CD-832; (b) diltiazem; (c) no treatment. CD-832 and diltiazem were added to the diet, in doses of 0.05 and 0.15% (approximately 30 and 100 mg/kg per day), respectively, throughout the experimental period. In untreated control SHRSPs, systolic blood pressure increased and severe renal lesions such as fibrinoid necrosis, smooth muscle proliferation, glomerular and tubular lesions and some cardiac fibrosis were observed at age 20 weeks. 12-week repeated-administration of CD-832 and diltiazem led to a comparable hypotension and decreased heart rate. CD-832 and diltiazem decreased the ratios of weights of kidney and heart to body weight and the concentration of blood urea nitrogen and creatinine in serum, compared to values in controls. In SHRSPs treated with CD-832 and diltiazem, the incidence of renal lesions and myocardial fibrosis was significantly reduced when compared with control SHRSPs. These results suggest that 12-week repeated-administration of CD-832 prevents the development of hypertension and the incidence of organ damage in SHRSPs. CD-832 and diltiazem were equally efficacious in preventing organ damage but this organ-protective effect was obtained at a lower dose for CD-832 (30 mg/kg per day) than that of diltiazem (100 mg/kg per day).

Relative selectivity for negative chronotropic and inotropic effects of a novel dihydropyridine derivative CD-832

The effects of CD-832 [(4R)-(-)-2-(nicotinoyl-amino) ethyl 3-nitroxypropyl 1,4-dihydro-2,6-dimethyl-4,3-nitrophenyl, 3,5-pyridine dicarboxylate], a novel dihydropyridine derivative, on various guinea-pig myocardial preparations were compared with those of nifedipine, verapamil and diltiazem. CD-832 decreased the action potential duration of isolated papillary muscles without substantially affecting other parameters. In voltage-clamped single ventricular myocytes, CD-832 decreased the L-type Ca2+ current amplitude while having little effect on outward currents. CD-832 and other Ca2+ channel antagonists produced negative chronotropic effects in isolated right atrial preparations and negative inotropic effects in right ventricular papillary muscles, respectively, in a concentration-dependent manner. The potency order for the negative chronotropic effect was CD-832 > nifedipine > verapamil > diltiazem, while that for the negative inotropic effect was nifedipine > verapamil > or = CD-832 > diltiazem. The ratio, EC20 for negative inotropic effect divided by EC20 for negative chronotropic effect, which was considered to be an index of selectivity for negative chronotropic effect was highest for CD-832, the ratio for CD-832, nifedipine, verapamil and diltiazem being 5.4, 0.11, 0.25 and 0.37, respectively. These results indicate that CD-832 is an L-type Ca2+ channel antagonist with relative selectivity for a negative chronotropic effect rather than for a negative inotropic effect. This 'chrono-selective' cardiosuppressive effect of CD-832 could be of value in the treatment of cardiovascular diseases such as angina pectoris.

Effects of CD-832, a dihydropyridine derivative with a nitrate ester moiety on rabbit femoral artery and vein

We investigated the effects of CD-832 ((4R)-(-)-2-(nicotinoyl-amino)ethyl 3-nitroxypropyl 1,4-dihydro-2,6-dimethyl-4,3-nitrophenyl, 3,5-pyridine dicarboxylate), a dihydropyridine derivative with a nitrate ester moiety, on contractile responses in rabbit femoral arteries and veins. CD-832 (10(-8) to 10(-6) M and nifedipine inhibited the 64 mM KCl-induced and 10(-6) M norepinephrine-induced contractions of rabbit femoral arteries, while nitro compounds had no effect on the contractions. CD-832 (10(-8) to 10(-6) M) and nitro compounds inhibited the 10(-6) M norepinephrine-induced contractions in rabbit femoral veins, while other Ca2+ channel antagonists had little effect. The inhibitory effects of CD-832 (10(-7) M) on norepinephrine-induced contractions were antagonized by treatment with methylene blue (10(-5) M). These results indicate that CD-832 potently relaxes venous smooth muscle, and that it may be a useful agent for the treatment of angina pectoris.