Benidipine is a dihydropyridine-derived calcium channel blocker developed in Japan, with several unique mechanisms of action, that is, triple calcium channels (L, N, and T) blocking action with a membrane approach. Benidipine has relatively high vascular selectivity and is expected to show protective effects on vascular endothelial cells. Renal protective effects of benidipine also have been shown in several basic and clinical studies. Moreover, anti-oxidative action and enhancing nitric oxide production have been noted with this drug, following its cardio-protective effects in patients with ischemic heart diseases. In fact, benidipine exerted a better prognostic effect than other calcium channel blockers in the therapy for patients with vasospastic angina. In addition, benidipine showed reliable antihypertensive, renoprotective effects if used in combination with angiotensin II type 1 receptor blockers (ARBs) when adequate anti-hypertensive effects are not achieved by ARBs alone, indicating that benidipine is an useful calcium channel blocker in combination therapy for hypertension. Benidipine was launched on the Japanese market 14 years ago, but few severe side effects have been reported, suggesting that this is a drug with established safety and long-acting pharmacological effects.
The thromboxane A2 receptor (TP), one of the G protein-coupled receptors (GPCRs), consists of two splicing variants, TPα and TPβ, which differ in their C-terminal regions. In the present study, we investigated whether TPα and TPβ formed homo- or hetero-dimers and whether the dimerization changed the function of TP. The immunofluorescent analysis using human embryonic kidney (HEK) 293 cells expressing either FLAG-tagged TPα or TPβ showed that TPα is mainly distributed on plasma membranes and TPβ existed on plasma membranes and within the cells. Co-immunoprecipitation analysis using HEK293 cells expressing both TPα and TPβ showed that TPα and TPβ formed homo- and hetero-dimers. U46619, a TP agonist, caused phosphoinositide hydrolysis and elevation of [Ca2+]i in a concentration-dependent manner in Chinese hamster ovary (CHO) cells expressing TPα or TPβ. The responses were observed to a greater extent in the cells expressing TPα than TPβ. In the cells expressing both TPα and TPβ, U46619-induced responses were observed to a lesser extent than in the cells expressing TPα alone. Furthermore, [3H]SQ29548 binding showed that the level of the cell surface expression of TP was the following order: the cells expressing TPα > TPα and TPβ > TPβ. These results indicate that TPα and TPβ formed homo- and hetero-dimers, and TP-mediated signaling may be regulated by the hetero-dimer.
The present work was designed to observe the influences of arterial baroreflex (ABR) function on cardiovascular effects produced by four routinely used antihypertensive drugs in conscious rats. A low ABR model was obtained by the performance of sinoaortic denervation (SAD). The doses of the four drugs were as follows: nifedipine (1.5, 3.0 mg/kg), captopril (50, 100 mg/kg), atenolol (10, 20 mg/kg), and hydrochlorothiazide (20, 40 mg/kg). They were administered via an intra-gastric catheter. Compared with sham-operated rats, SAD significantly increased blood pressure variability about 2 times without modification of blood pressure level. The decrease in blood pressure level induced by the four tested drugs was larger in SAD rats than in sham-operated rats, which decreased to about 10 mmHg. Pulse interval was not changed by the treatment of captopril, but prolonged by atenolol in both sham-operated and SAD rats. In sham-operated groups, treatment of both nifedipine and hydrochlorothiazide decreased pulse interval. Whereas in sinoaortic denervated ones, this tachycardia was prevented. Among the four tested drugs, it was found that only nifedipine and atenolol significantly decreased blood pressure variability in SAD rats. It can be concluded that arterial baroreflex function was able to attenuate the hypotensive effects produced by antihypertensive drugs in conscious rats.
One of the most important prognostic factors in the thrombolytic treatment of acute ischemic stroke is to recanalize. The purpose of this study was to evaluate the effectiveness and safety of urokinase in a primate thromboembolic stroke model. Thromboembolic stroke was accomplished via occlusion of the middle cerebral artery (MCA) obtained by injecting an autologous blood clot into the left internal carotid artery in 21 male cynomolgus monkeys. Animals were randomly assigned to the following treatment groups: Group 1: vehicle (saline), Group 2: urokinase (40,000 IU), Group 3: urokinase (120,000 IU,) over 2 or 6 h via intra-internal carotid catheter starting 1 h after embolization, respectively. In the urokinase-treated groups, neurologic deficits were improved in consciousness and skeletal muscle coordination, but not sensory and motor systems. The infarction size in Group 2 (11.9 ± 3.9% of the hemisphere) and 3 (7.6 ± 2.5%) were significantly smaller than that (24.7 ± 3.5%) in Group 1. However, 2 of 5 animals in Group 3 died. In conclusion, urokinase improved neurologic deficits and reduced cerebral infarction on thromboembolic stroke in the cynomolgus monkey.
To find the characteristics of scratching behavior in hairless mice (HR-1), compound 48/80 and some putative chemical mediators of allergic reaction were injected intradermally into the backs of mice, and the number of scratching behaviors was measured. As reference mice, NC/Nga, ICR, and ddY mice were used. Scratching behavior in HR-1 and ICR mice was increased dose-dependently by compound 48/80. The same result was also observed with NC/Nga and ddY mice. However, the response in NC/Nga and ddY mice was far less than those of HR-1 and ICR mice. Similar to NC/Nga and ddY mice, HR-1 mice showed less sensitivity to histamine than ICR mice. On the other hand, the HR-1 mice showed a high response to serotonin compared with those of the NC/Nga and ddY mice. The scratching behavior in HR-1 mice induced by substance P was increased, but the effect was less potent than those in NC/Nga, ICR, and ddY mice. These results suggest that the scratching behavior induced by compound 48/80 in HR-1 mice is mainly attributable to serotonin.
Dimethylsphingosine (DMS) was first reported as an inhibitor of protein kinase C and later has been used as a specific inhibitor of sphingosine kinase. Furthermore, its anti-cancer effect has become a basis for development of chemotherapy. Nevertheless, its anti-neoplastic mechanism has poorly been understood. In the present study, we observed that DMS increased intracellular pH and Ca2+ concentration in U937 human monocytes. To further characterize these DMS-induced actions, we employed structurally-related sphingolipids and specific pharmacological tools such as inhibitors of protein kinase C and Na+/H+ exchanger and found that the two responses of DMS were mimicked by four stereoisomers of sphingosine and two isomers to dihydrosphingosine, but not with sphingosine 1-phosphate, sphingosyl-phosphorylcholine, and C2-ceramide. Furthermore, DMS-induced pH increase was independent of Na+/H+ exchanger activity. We also characterized the interrelationship between DMS-induced pH increase and DMS-induced Ca2+ increase. Since DMS is considered to be a good anti-cancer candidate, our characterization of DMS actions provides useful information for development of DMS chemotherapy.
The purpose of the present study was to investigate the involvement of chemical mediators, other than histamine, in the scratching behavior induced by H3 antagonists. Scratching behavior was induced by the histamine H3 antagonists iodophenpropit and clobenpropit (10 nmol/site) when they were injected intradermally into the rostral part of the back of mast-cell-deficient (WBB6F1 W/Wv) and wild-type (WBB6F1 +/+) mice. Subsequently, the effect of spantide, a tachykinin NK1 antagonist, was measured for 60 min. The effects of the H3 antagonists on in vitro histamine release from rat peritoneal mast cells were also investigated. When spantide was injected intradermally at a dose of 0.5 nmol/site, it significantly inhibited the response. Furthermore, iodophenpropit and clobenpropit (10−6 – 10−8 M) did not induce histamine release in isolated rat peritoneal mast cells. Our results indicate that substance P is involved in the skin responses elicited by the histamine H3 antagonists. Moreover, the fact that these histamine H3 antagonists did not induce significant increases in the histamine release from rat peritoneal mast cells suggests that the histamine H3 receptor may not be present in the peripheral cells considered in this study.
Lengthening of the effective refractory period (ERP) by EGIS-7229, a class III/Ib/IV drug, and by dofetilide, a selective IKr blocker, was compared in normokalemia (NK), hypokalemia (LK), and hyperkalemia (HK) in right ventricular papillary muscles of rabbits paced at 0.5, 1, and 2 Hz, in vitro, and also during β-adrenergic activation. In NK, EGIS-7229 (3 and 10 μM) and dofetilide (30 and 100 nM) similarly lengthened ERP in a steeply reverse frequency-dependent manner. The two compounds produced smaller ERP prolongations at 0.5 Hz in HK and LK, so rate-dependence of ERP changes decreased. EGIS-7229 lengthened ERP more at 2 Hz than at 0.5 Hz at 10 μM in LK, that is, the effect of EGIS-7229 turned into positive frequency-dependence from 3 to 10 μM. Furthermore, EGIS-7229 lengthened ERP at 10 μM more than dofetilide at 100 nM at 2 Hz stimulation rate (P<0.05). Isoproterenol (30 nM) eliminated the effect of dofetilide on ERP, while EGIS-7229 prolonged ERP during β-adrenergic activation. In conclusion, efficacy of EGIS-7229 was superior to that of dofetilide in LK and during β-adrenergic stimulation, suggesting improved antiarrhythmic action for EGIS-7229 under certain conditions in the patient.
This study investigated whether carbamazepine could produce local peripheral antinociception in a rat model of inflammatory mechanical hyperalgesia, and whether adenosine receptors are involved. Carbamazepine (100 – 1000 nmol/paw) coadministrated with a pro-inflammatory compound, concanavalin A, into the hind paw caused a significant dose- and time-dependent anti-hyperalgesia. Coadministration of caffeine (250 – 1000 nmol/paw), a nonselective adenosine-receptor antagonist, as well as DPCPX (10 – 30 nmol/paw), a selective adenosine A1-receptor antagonist, with carbamazepine, significantly depressed its anti-hyperalgesic effect. Drugs injected into the contralateral hind paw did not produce significant effects. These results suggest that carbamazepine produces local peripheral anti-hyperalgesia via peripheral adenosine A1 receptors.