Novel LC-MS/MS method for simultaneous quantification of KW-7158, a new drug candidate for urinary incontinence and bladder hyperactivity, and its metabolites in rat plasma: a pharmacokinetic study in male and female rats.

To investigate the pharmacokinetics of KW-7158 (CAS 214763-95-8), a new drug candidate for urinary incontinence and bladder hyperactivity, in male and female rats, we developed and validated a simultaneous quantification method for KW-7158 and its 2 metabolites, M1 and M2, in plasma using high performance liquid chromatography-tandem mass spectrometry with positive/negative ion-switching scan mode. The method was selective and sensitive to KW-7158, M1 and M2 with overall precision expressed as coefficient of variance less than 11.8% and accuracy (relative error) within ± 13.7% in intra- and inter-assay variability. This method was used to determine the plasma concentration of KW-7158, M1 and M2 after intravenous and oral administration of KW-7158 in male and female rats. KW-7158 was detected as a primary constituent in plasma in both administration routes. M1 was a major metabolite with the concentration ratio of 10-20% of KW-7158, and M2 was a minor metabolite. Pharmacokinetics of KW-7158 after oral administration was considered to be linear at doses from 0.01 to 1 mg/kg. Bioavailability was relatively high with the values of 69.4 ± 17.1% and 82.6 ± 20.0% at a dose of 0.1 mg/kg in male and female rats, respectively. There was a little gender difference in pharmacokinetics of KW-7158 and its metabolites in rats.

Purification and properties of rabbit muscle proteasome, and its effect on myofibrillar structure.

This paper describes the purification and properties of a multicatalytic proteinase complex, proteasome, from rabbit skeletal muscle, and its effect on myofibrillar structure. The purified proteasome gave a single band on polyacrylamide gel electrophoresis under non-denaturing conditions and gave eight bands under denaturing conditions, indicating that this enzyme comprises multiple hetero-subunits with low molecular mass. The purified proteasome was not activated by ATP and ubiquitin, and was markedly inhibited by Z-Leu-Leu-Leu-H (aldehyde). These data indicate that the purified proteasome is not 26S, but 20S. The proteasome degraded synthetic peptides maximally at pH 8.0. Relative to pH 8.0, activities were gradually decreased with the lowering of pH, but the degree of decrease was substrate-dependent, and the activity at pH 5.0 still retained about 30~60% of the activity at pH 8.0, indicating the possibility that the proteasome is active in the muscle during conditioning. When the proteasome was heated at 60 °C for 20 min and treated in the presence of 0.005% SDS, the activity increased over 1.5 and 4.5 times, respectively. SDS remarkably increased the V(max) value of the enzyme at pH 8.0. The proteasome was also activated by high hydrostatic pressure up to 100~150 M Pa and gradually decreased at 200 MPa or higher. Electron microscopic observation revealed that obvious gaps between filamentous structure, the complete loss of M-line and partial loss of Z-line structure were caused by proteasome.

A beamline for photochemical processes at atmospheric pressure.

A beamline especially designed for atmospheric photochemical reactions has been constructed at the NTT synchrotron radiation facility. By inserting a buffer helium chamber with Be and Si(3)N(4) partition windows between the beamline and the reaction chamber, studies can be performed without the differential pumping systems normally used in existing photochemistry beamlines. The reaction chamber is equipped with a gas supply system and analysis systems to investigate gas-phase and surface reactions. Purging using dry purified gases in combination with water-bubbling gives effective control of water concentration in the reaction chamber.

Disposition and metabolism of KW-2149, a novel anticancer agent.

KW-2149 is a new derivative of mitomycin C (MMC). The plasma concentrations, distribution, metabolism, and excretion of [3H]-KW-2149 in normal and tumor-bearing mice after i.v. administration of 16.6 mg/kg were investigated. The plasma radioactivity decreased biexponentially after i.v. administration in normal mice. However, the unchanged drug disappeared rapidly, showing a half-life (t1/2) of 9.7 min, which was shorter than MMC's (18 min). The radioactivity was excreted in mouse urine (33%) and feces (58%) within 144 h. High radioactivity was distributed in the gallbladder, liver, kidney, pancreas, and lung at 1 h after i.v. administration to normal mice. The tumor concentration was lower than the plasma or blood concentration. The lowest radioactivity was observed in the brain. The metabolic rate of KW-2149 was very rapid. The methyl sulfide form (M-16), the symmetrical disulfide dimer (M-18), and the albumin conjugate were detected in plasma, which possessed anticellular activity. The specific anticellular activity of these compounds against uterine carcinoma (HeLa S3) was 1/100, 1, and 1/20 respectively, as compared with that of KW-2149.