Antiaggregatory, antithrombotic effects of MS-180, a novel platelet glycoprotein IIb/IIIa receptor antagonist.

The antiaggregatory and antithrombotic effects of (S)-(-)-ethyl[6-[4-(morpholinoformimidoyl)benzamido]-3,4-dihydro-2 H-1-benzo-pyran-3-yl]acetate hydrochloride (MS-180), a novel platelet glycoprotein IIb/IIIa receptor antagonist, were investigated. Ma-HCl, (S)-(-)-[6-[4-(Morpholinoformimidoyl)benzamido]-3,4-dihydro-2H-1-b enzopyran-3-yl]acetic acid hydrochloride, the hydrochloride salt of Ma (active metabolite), inhibited the binding of fibrinogen to immobilized human glycoprotein IIb/III receptor with an IC50 value of 0.12+/-0.03 nM without affecting binding to either fibronectin or vitronectin receptors. In anesthetized guinea pigs, intraduodenal administration of MS-180 caused dose-dependent inhibition of both ADP- and collagen-induced ex vivo platelet aggregation. At the same dosages, occluded thrombus formation and platelet release reactions were also markedly suppressed. In anesthetized dogs, the bleeding time was prolonged slightly even when submaximal inhibition (< 90%) of ex vivo platelet aggregation was achieved following i.v. administration of Ma-HCl. Aspirin (100 mg/kg) prolonged the bleeding time to the same extent as MS-180 (1 mg/kg), although it suppressed only collagen-induced platelet aggregation. Therefore, MS-180 may be clinically useful for the treatment of thrombotic diseases.

The neuroprotective agent MS-153 stimulates glutamate uptake.

We investigated the effect of (R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153), a novel neuroprotective agent, on L-[3H]glutamate uptake through GLT-1, a Na(+)/K(+)-dependent glial glutamate transporter, expressed in COS-7 cells. MS-153 (1-100 microM) accelerated the L-[3H]glutamate uptake through GLT-1 in a concentration-dependent and time-dependent manner. Eadie-Hofstee analysis revealed that MS-153 significantly decreased the K(m) of the glutamate uptake by COS-7 cells expressing GLT-1. In contrast, [3H]gamma-aminobutyric acid (GABA) uptake through a glial GABA transporter was not affected. In addition, MS-153 increased Na(+) currents through GLT-1 expressed in Xenopus oocytes. We also investigated the effect of MS-153 on amino acid efflux from rat hippocampal slices. The increase in glutamate efflux induced by 50 mM KCl was significantly attenuated by the treatment with MS-153 at 10 microM, while MS-153 had no significant effect on the K(+)-evoked efflux of GABA. Furthermore, the increase in glutamate efflux by ischemia (hypoxia/aglycemia) was partially, but significantly inhibited by MS-153. These results suggest that the cerebroprotective effect of MS-153 in this ischemic model in vivo is due to the specific reduction of the glutamate concentration in the extracellular space, which can probably be attributed to the acceleration of glutamate uptake by the indirect modulation of the glutamate transporter activity.

Respiratory effects of halothane and AMPA receptor antagonist synergy in rats.

The influence of N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor antagonists in combination with halothane anaesthesia on the respiratory system was investigated. Under 1.5% halothane anaesthesia, respiratory parameters including respiratory rate, minute volume, tidal volume, inspiratory and expiratory duration were measured before and after drug administration in rats. The AMPA receptor antagonists, 6-(1H-imidazol-1-yl)-7-nitro-2,3-(1H,4H)-quinoxalinedione hydrochloride, YM90K (5 and 10 mg/kg) and 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX, 15 mg/kg), which were administered intravenously for 30 min, significantly reduced the respiratory rate (P < 0.01) and minute volume (P < 0.01) and increased the tidal volume (P < 0.05) compared with values obtained before drug administration. None of these drugs affected respiratory parameters in the absence of anaesthesia. A NMDA receptor antagonist, MK-801 (0.5 mg/kg), which was administered intravenously for 30 min, also significantly reduced respiratory rate (P < 0.01), minute volume (P < 0.01) and tidal volume (P < 0.01) and prolonged inspiratory duration (P < 0.05). These results suggest that both AMPA and NMDA receptor antagonists cause respiratory depression under halothane anaesthesia in rats, although the mechanisms may be different for the two types of antagonists.

Inclusion of trithia[5]heterohelicene by various serum albumins. An effective probe for chiral discrimination.

Racemic 2-hydroxymethyltrithia[5]heterohelicene (2-HT), which has a labile helical structure was incorporated into serum albumins of nine species in 1% ethanolic aqueous solution, giving 1:1 complexes which exhibited induced circular dichroism spectra with species specificity. The application of 2-HT to bovine serum as a probe for chiral recognition revealed that the serum itself manifested an apparent chiral discrimination between enantiomers of 2-HT.

Cerebroprotective effects of a novel pyrazoline derivative, MS-153, on focal ischemia in rats.

MS-153 ((R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline) is a novel pyrazoline compound that has potent cerebroprotective effects in the rat focal cerebral ischemia model. Middle cerebral artery (MCA) occlusion in rats allows detailed assessment of both functional and morphological sequelae of brain infarct. Using this model, we evaluated the cerebroprotective effects of MS-153. Treatment with MS-153 (12.5 mg/kg, i.v. bolus followed by 6.25 mg/kg/hr or 25.0 mg/kg, i.v. bolus followed by 12.5 mg/kg/hr infusion for 7 days) significantly reduced infarct volumes and improved neurological deficits in MCA occluded rats 7 days after occlusion. Delayed treatment significantly reduced infarct volume 24 hr after MCA occlusion when MS-153 (25.0 mg/kg, i.v. bolus followed by 12.5 mg/kg/hr infusion for 21 hr) administration was started 3 hr after occlusion. Brain edema was also significantly improved when MS-153 (25.0 mg/kg, i.v. bolus followed by 12.5 mg/kg/hr infusion for 18 hr) administration was started 6 hr after occlusion.

23Na- and 1H-NMR studies of the action of chlorpromazine and imipramine on nigericin-mediated Na+ transport across phosphatidylcholine vesicular membranes.

In order to elucidate the action of chlorpromazine (CPZ) and imipramine (IMP) on nigericin-mediated Na+ transport across phosphatidylcholine vesicular membranes, 23Na nuclear magnetic resonance was applied to the exchange system of Na+ ions present at the same concentration inside and outside unilamellar vesicles. CPZ and IMP added to the vesicles in micromolar concentrations produced an equal increase in the carrier-transport rate. The kinetic analysis, together with 1H-NMR observations of the reduction in membrane fluidity produced by the drugs and on the direct interaction between drugs and nigericin, allowed us to conclude that the drug-induced promotion of transport occurred not from the formation step of the Na(+)-nigericin complex nor from its diffusion step, but from its dissociation step. The formation of an adduct between drug and nigericin could be the cause of the drug effect and this proceeded much more efficiently at a membrane-water interface (stability constant Kb; 3 x 10(5) M-1) than in methanol (Kb; 5 x 10(2) M-1). The reason for the difference is also discussed.

Radical scavenger effect of Boschniakia rossica.

To elucidate the mechanism of the invigorating and antisenile action of the dried herb of Boschniakia rossica (Boschniakiae Herba), the free radical scavenging activity of its 50% ethanol extract (BR) was examined using an electron spin resonance spectrometer. The scavenging activity of plasma from Fisher-334 rats with continuous administration of BR was also examined. The concentrations showing 50% inhibition of the free radical of BR on the 1,1-diphenyl-2-picrylhydrazil (DPPH) radical, superoxide radical and hydroxyl radical were 0.003%, 0.06% and 9.67%, respectively. Plasma from the rats with BR administered clearly showed higher free radical scavenging activity compared with that of normal control rats. These findings suggest that Boschniakia rossica has strong free radical scavenging activity and consequently it has inhibitory effects on the disorders caused by free radical production in living tissue.

23Na and 1H NMR studies on melittin channels activated by tricyclic tranquilizers.

A dynamic 23Na nuclear magnetic resonance (NMR) technique was applied to the exchange system of Na+ ions present inside and outside large unilamellar vesicles at an equivalent concentration. Addition of melittin to phosphatidylcholine vesicles did not induce any detectable Na+ transport across the membrane but subsequent addition of a trace of chlorpromazine or imipramine did induce Na+ transport. Because the formation of a drug-melittin adduct in a solution was detected by 1H NMR, the activation of melittin channels was assumed to originate from the direct interaction of the drug and melittin.

Magnetic resonance studies on the copper site of dopamine beta-monooxygenase in the presence of cyanide and azide anions.

In order to elucidate the coordination state of water molecules in the Cu(II) site of dopamine [( 3,4-dihydroxyphenyl)ethylamine] beta-monooxygenase, measurements of the paramagnetic 1H nuclear magnetic relaxation rate of solvent water in the enzyme solution containing cyanide or azide as an exogenous ligand were carried out to obtain the values of intrinsic paramagnetic relaxation rate decrements Rp1 and Rp2 for the ligand-enzyme 1:1 and 2:1 complexes, respectively. Rp1 (percent) values were 53 (pH 5.5) and 52 (pH 7.0) for cyanide and 38 (pH 5.5) and 32 (pH 7.0) for azide, while Rp2 (percent) values were 98 (pH 5.5) and 96 (pH 7.0) for azide. Although no Rp2 values for cyanide were obtained because of its reducing power at the Cu(II) site, the Rp1 and Rp2 values obtained above prove that the Cu(II) center has two coordinated water molecules that are exchangeable for exogenous ligands at either pH. Supporting evidence was provided by electron paramagnetic resonance (EPR) titration, in which the enzyme solution containing cyanide-enzyme (1:1) complex in an equal proportion to uncomplexed enzyme gave an observed paramagnetic relaxation rate decrement, Rp, of 23%. Another characteristic of the Rp1 and Rp2 values was their invariability with respect to pH, indicating that the three-dimensional structure of the Cu(II) site is pH-invariant within the range examined. Binding constants of ligand to enzyme Kb1 and Kb2 for 1:1 and 2:1 complex formation, respectively, were also determined through an analysis of the Rp values; it was found that Kb1 was larger than Kb2 irrespective of pH. (ABSTRACT TRUNCATED AT 250 WORDS)