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R Ishida

Publications and source records attributed to R Ishida.

At least 19 recordsLinked to original sources
PubMed1992

Enzymatic basis for the non-linearity of hepatic elimination of propranolol in the isolated perfused rat liver.

Propranolol (PL) metabolism was studied in the isolated perfused rat liver under single-pass and steady-state conditions. An attempt was made to predict the data observed in the isolated rat liver perfusion at PL infusion rates of 89-1317 nmol/min using the microsomal kinetic parameters obtained in our previous paper (Ishida et al., Biochem Pharmacol 43: 2489-2492, 1992) and the unbound PL fractions in rat liver microsomes and the perfusion medium. The values of kinetic parameters obtained in rat liver microsomes were corrected for the whole liver. Two groups of cytochrome P450 isozymes having high (Km < 0.5 microM)- and low (Km > 20 microM)-affinities participate in the metabolism of PL and sudan III pretreatment induces the low-affinity enzymes rather than the high-affinity enzymes in control rats. Of high-affinity isozyme(s) PL 4-hydroxylase and 7-hydroxylase made a major contribution to the overall activity, while for low-affinity isozymes PL 4-hydroxylase and N-desisopropylase did. A nonlinear relationship between the PL concentrations entering and leaving the liver was predicted from these corrected kinetic parameters using the venous equilibrium model. The outflow concentrations and the metabolic rates of PL for the predicted curves were over-estimated at higher inflow PL concentrations and under-estimated at higher substrate concentrations, respectively. On the other hand, the prediction for them was successfully carried out for the livers whose intrinsic clearance was altered due to the induction of low-affinity enzymes in PL metabolism by sudan III pretreatment. The outflow rates of 4-hydroxypropranolol showed a downward curvature at lower substrate concentrations, followed a linear rise in the livers from control rats, while the outflow rates of 5- and 7-hydroxypropranolol exhibited their respective limiting values. The outflow rates of 4-hydroxypropranolol and N-desisopropylpropranolol were enhanced markedly with increasing the outflow unbound concentration of PL by sudan III pretreatment. These results indicate that non-linear PL first-pass metabolism is due to the saturation of the reactions for the high-affinity enzymes among enzymes engaging in PL ring hydroxylations.

Animals↗
PubMed1992

Induction of propranolol metabolism by the azo dye sudan III in rats.

Effects of the azo dye sudan III, an inducer of cytochrome P450 isozymes belonging to the CYP1A subfamily, on propranolol (PL) in vitro and in vivo metabolism were investigated in rats. The kinetic parameters of the activity for each metabolic pathway were determined in liver microsomes from control and sudan III-treated rats. Sudan III pretreatment increased extensively PL 4-hydroxylase, 5-hydroxylase and N-desisopropylase activities at high but not at low PL concentrations. On the other hand, kinetic parameters of 7-hydroxylase activity were not affected by sudan III pretreatment. Sudan III pretreatment decreased blood concentrations of PL after intraportal infusion of PL at high doses (12.5 and 20 mg/kg), but not at a low dose (5 mg/kg). These observations were consistent with data obtained from the in intro studies showing that sudan III pretreatment induced low-affinity but not high-affinity cytochrome P450 isozymes involved in PL metabolism in rat liver microsomes.

Animals↗
PubMed1992

Effect of ICRF-193, a novel DNA topoisomerase II inhibitor, on simian virus 40 DNA and chromosome replication in vitro.

The effect of ICRF-193, a noncleavable-complex-forming topoisomerase II inhibitor, on simian virus 40 (SV40) DNA and SV40 chromosome replication was examined by using an in vitro replication system composed of HeLa cell extracts and SV40 T antigen. Unlike the topoisomerase inhibitors VP-16 and camptothecin, ICRF-193 had little effect on DNA chain elongation during SV40 DNA replication, but high-molecular-weight DNAs instead of segregated monomer DNAs accumulated as major products. Analysis of the high-molecular-weight DNAs by two-dimensional gel electrophoresis revealed that they consisted of catenated dimers and late Cairns-type DNAs. Incubation of the replicated DNA with topoisomerase II resulted in conversion of the catenated dimers to monomer DNAs. These results indicate that ICRF-193 induces accumulation of catenated dimers and late Cairns-type DNAs by blocking the decatenating and relaxing activities of topoisomerase II in the late stage of SV40 DNA replication. In contrast, DNA replication of SV40 chromosomes was severely blocked by ICRF-193 at the late stage, and no catenated dimers were synthesized. These results are consistent with the finding that topoisomerase II is required for unwinding of the final duplex DNA in the late stage of SV40 chromosome replication in vitro.

Camptothecin↗
PubMed1992

Effects of long-term administration of (4S)-1-methyl-3-[(2S)-2-[N-((1S)-1-ethoxycarbonyl-3- phenylpropyl)amino]propionyl]-2-oxoimidazolidine-4-carboxylic acid hydrochloride (TA-6366), a new angiotensin I converting enzyme (ACE) inhibitor, from the pre-hypertensive stage on morphological change and mechanical property related to sodium ion permeability in aorta of spontaneously hypertensive rats (SHRs).

Effects of (4S)-1-methyl-3-[(2S)-2-[N-((1S)-1-ethoxycarbonyl-3-phenylpropyl)amino]- propionyl]-2-oxoimidazolidine-4-carboxylic acid hydrochloride (TA-6366) on morphological change and mechanical property related to sodium ion permeability in the aorta of spontaneously hypertensive rats (SHRs) were examined, as compared with those of enalapril and captopril. Ten-week oral administration of TA-6366 (1 and 5 mg/kg/d) from 4 weeks of age impeded aortic media-thickening together with a rise in blood pressure in SHRs. Concomitantly, aorta weights in both groups were markedly decreased. The higher dose of TA-6366 almost fully suppressed the accelerated tension development induced by K(+)-free medium and decreased total sodium ion content in the aorta. These vascular effects of TA-6366 was more prominent than those of enalapril and captopril at 5 mg/kg/d. The difference in potencies on the above vascular parameters between TA-6366 and these drugs seemed to be mainly related to the difference in their antihypertensive activities. These results suggest that TA-6366 has preventive effects against progression of vascular diseases, particularly atherosclerosis, accompanied with hypertension.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Studies on angiotensin converting enzyme inhibitors. VI. Synthesis and angiotensin converting enzyme inhibitory activities of the dicarboxylic acid derivative of imidapril and its diastereoisomers.

All possible diastereoisomers of the dicarboxylic acid (10a), the biologically active form of imidapril (1), were synthesized, and their inhibitory activity against angiotensin converting enzyme (ACE) was examined. The in vitro ACE inhibitory activity of these compounds greatly depended on the configurations of the three asymmetric carbons in each molecule. The (S,S,S) isomer (10a) showed much more potent activity than the others.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Identification of urinary metabolites of 2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine in rat, rabbit and dog.

The metabolism of KC-764 (2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine, CAS 94457-09-7) in rat, rabbit and dog was studied. The urine of animals dosed with 14C-KC-764 was extracted with ethyl acetate after treatment with beta-glucuronidase and arylsulfatase. The metabolites were purified by TLC and HPLC from the extract. Unchanged KC-764 and 16 metabolites were isolated and their structures were identified or proposed by NMR and MS spectrometry. The metabolism of KC-764 took place by the oxidation of the tetrahydropyridine ring, 6,7-position and 2-methyl group of the pyrazolopyridine ring, and their combinations. The oxidation of the tetrahydropyridine ring was predominant in dog, whereas the oxidation of the pyrazolopyridine ring was more important in rabbit. Rat produced the various metabolites by their combination. 6-Oxo and 6-ureido derivatives of the tetrahydropyridine ring were common major metabolites in all animal species studied.

Animals↗
PubMed1992

Pharmacokinetics of the new antiplatelet agent 2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine in laboratory animals.

KC-764 (2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo [1,5-a]pyridine CAS 94457-09-7) and its metabolites in serum and urine were determined after intravenous and oral administration in mice, rats, rabbits and dogs at a dose of 5 mg/kg. KC-764 was rapidly eliminated from serum in all species. The biological half-lives of unchanged KC-764 after intravenous administration in mice, rats, rabbits and dogs were 1.31, 0.29, 1.94 and 1.20 h, respectively. 2-Methyl-3-(1,4,5,6-tetrahydro-6-oxonicotinoyl)pyrazolo-[1,5-a]pyr idine was a common major metabolite in serum of all species, although 6,7-dihydro-6,7-dihydroxy-2-methyl-3-(1,4,5,6- tetrahydro-6-oxonicotinoyl) pyrazolo-[1,5-a]pyridine (M-8) was more abundant in rabbits. Urinary recovery of unchanged KC-764 was as low as 0.4-2.2% in all species. The major urinary metabolite was 2-methyl-3-(1,4,5,6-tetrahydro-6-ureidonicotinoyl)pyrazolo-[1,5-a] pyridine in mice, rats and dogs, but M-8 was in rabbits. KC-764 was rapidly and well absorbed by oral administration, and extensively metabolized in all species tested.

Administration, Oral↗
PubMed1992

Pharmacokinetics of the new antiplatelet agent 2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine in human subjects.

The pharmacokinetics of KC-764 (2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine, CAS 94457-09-7) was studied in healthy male adult volunteers after single ascending oral dose and multiple dosing for 7 days. Serum KC-764 concentration attained the peak in 1 h and declined with a half-life of about 2 h at a single oral dose of 5, 10, 20 and 40 mg. No dose dependent pharmacokinetics of KC-764 was demonstrated. Three metabolites were detected in serum, but their concentrations were lower than that of KC-764. 48-h urinary recoveries after single doses were 41.6-46.6% of dose, not being dose-dependent. Urinary recovery of unchanged KC-764 was 1.1-1.6% of dose. Three metabolites were present in greater amount in urine than unchanged KC-764 and two metabolites were less than KC-764. There was little daily variation of serum concentrations and urinary excretion of KC-764 and its metabolites in the multiple dosing (20 mg twice a day) study. The daily and total urinary recovery were same as those after single doses. Food reduced Cmax and tended to delay tmax, but did not influence AUC0----infinity and urinary recovery. Serum protein binding of KC-764 was about 60%, being not dependent on total serum concentration.

Adult↗
PubMed1992

Effects of the new angiotensin-I-converting enzyme inhibitor imidapril on the responses of isolated vascular preparations to various agonists.

Effects of imidapril hydrochloride ((-)-(4S)-3-[(2S)-2-[[(1S)-1- ethoxycarbonyl-3-phenylpropyl]amino]propionyl]-1-methyl-2- oxoimidazolidine-4-carboxylic acid hydrochloride, imidapril, TA-6366, CAS 89396-94-1), a new prodrug type angiotensin converting enzyme (ACE) inhibitor, and 6366 A (CAS 89371-44-8), an active metabolite of imidapril, on isolated vascular preparations were studied. 6366 A inhibited angiotensin I (AT-I)-induced contraction of the rabbit thoracic aorta at 3 x 10(-10) mol/l or more and augmented bradykinin (BK)-induced relaxation of the dog renal artery precontracted with prostaglandin F2 alpha PGF2 alpha at 10(-9) mol/l or more, whereas imidapril at 10(-7) mol/l did not affect these responses. However, 6366 A, like imidapril, had no effect on angiotensin II (AT-II), norepinephrine, serotonin-, KCl- and PGF2 alpha-induced contractions. The inhibitory effect of 6366 A on AT-I-induced contraction was attenuated by denudation of the endothelium, but it was still maintained even after washing out the aorta that had been previously exposed to the medium containing 6366 A. This suggests that 6366 A persistently inhibits the angiotensin I converting enzyme located preferentially in the endothelium. Therefore, the antihypertensive action of imidapril is mainly attributable to the vasodilation through the inhibitory effects of 6366 A on AT-II synthesis and BK degradation in the vasculature.

Angiotensin I↗
PubMed1991

Inhibition of topoisomerase II by antitumor agents bis(2,6-dioxopiperazine) derivatives.

Several recently developed derivatives of bis(2,6-dioxopiperazine) have been shown to be new antitumor agents and are currently under clinical trials. We found that the mother compound of the bis(2,6-dioxopiperazine)s, ICRF-154, and its derivatives, ICRF-159, ICRF-193, and MST-16, are all inhibitors of mammalian type II DNA topoisomerase. By decatenation assay using kinetoplast DNA from Crithidia fasciculata, inhibition of purified calf thymus topoisomerase II by these compounds was investigated. Potency of inhibition was in the following order: ICRF-193 greater than ICRF-154 = ICRF-159 greater than MST-16. The doses giving 50% inhibition were 2, 13, 30 and 300 microM, respectively, for these compounds. ICRF-193, the most potent inhibitor, however, did not inhibit topoisomerase I at concentrations up to 300 microM. Addition of excess enzyme, but not of the substrate DNA, overcame the inhibition by ICRF-193. The drug did not stimulate the formation of cleavable complex between DNA and the enzyme. Furthermore, ICRF-193 even inhibited the formation of enzyme-mediated DNA cleavage induced by etoposide or 4'-[9-acridinylamino)methanesulfon-m-anisidide. These observations, together with the finding that ICRF-193 did not intercalate into DNA, suggest that ICRF-154 and related compounds are specific inhibitors of topoisomerase II with different modes of action: i.e., they interfere with some step(s) before the formation of the intermediate cleavable complex in the catalytic cycle. This is a property quite distinct from previously known cleavable complex-forming type topoisomerase II-targeting antitumor agents such as acridines, anthracyclines, and epipodophyllotoxins, but rather, mechanistically similar to the recently reported group of inhibitors that includes merbarone, aclarubicin, and fostriecin.

Antineoplastic Agents↗
PubMed1991

Inhibition of intracellular topoisomerase II by antitumor bis(2,6-dioxopiperazine) derivatives: mode of cell growth inhibition distinct from that of cleavable complex-forming type inhibitors.

In the accompanying paper (K. Tanabe, Y. Ikegami, R. Ishida, and T. Andoh, Cancer Res., 51: 4903-4908, 1991), we showed that ICRF-154 and -193, dioxopiperazine derivatives, inhibited the activity of purified topoisomerase II, without formation of a cleavable DNA-protein complex. In order to see whether ICRF-154 and ICRF-193 affect cellular topoisomerase II in situ or not, we examined the effect of these drugs on etoposide (VP-16)-induced, topoisomerase II-mediated DNA breaks in RPMI 8402 cells by alkaline sedimentation analysis. When RPMI 8402 cells were exposed to VP-16 in the presence of ICRF-154 or ICRF-193 for 1 h, VP-16-induced DNA strand breaks were greatly inhibited by both ICRF compounds. In parallel with this observation, VP-16-induced growth inhibition was also reversed by ICRF-193. Exposure of cells to ICRF-154 resulted in a progressive accumulation of cells with 4C DNA content. Although mitotic index did not significantly increase, mitotic abnormalities were seen in cells exposed to ICRF-193 or ICRF-154: all mitotic cells exhibited early mitotic figures with fewer condensed and entangled chromosomes. The most sensitive phase of the cell cycle to ICRF-154 was the G2-M. ICRF-154 did not affect the spindle formation. However, abnormally oriented spindles were observed in drug-treated cells in parallel with the appearance of multinucleated cells. The results suggest that ICRF-154 and -193 inhibit topoisomerase II activity in RPMI 8402 cells, and this effect resulted in the appearance of cells in G2 and early M phase with fewer condensed and entangled chromosomes and of cells with multilobed nuclei.

Cell Cycle↗
PubMed1991

Pharmacological studies on TA-6366, a new ACE inhibitor: II. Effect of long-term administration from the pre-hypertensive stage on blood pressure, relative heart weight and ACE activity of various tissues in spontaneously hypertensive rats (SHRs).

The long-term oral administration of TA-6366 (5 mg/kg/day) from 4-weeks old impeded the genetic hypertension development with only a slight decrease in heart rate in spontaneously hypertensive rats (SHRs). However, the lower dose (1 mg/kg/day) of TA-6366 did not affect the development, but it lowered blood pressure after the development was almost accomplished. Concomitantly, relative heart weights in both the groups were markedly decreased to almost the same degree. The reduction of ACE activity in the aorta, brain and lung of both groups was found at 24 hr after the final administration, particularly at the 5 mg/kg/day dose; and that of the aorta was kept at almost the same low level even on the 9th day after withdrawal. After withdrawal of TA-6366 (5 mg/kg/day), the significant decrease in blood pressure was sustained at least for 10 weeks. The beneficial effect of TA-6366 on the hypertension development in SHRs seems to be related to its strong and long-lasting ACE inhibition, especially in the vasculature.

Administration, Oral↗
PubMed1979

Studies on biologically active halogenated compounds. 1. Synthesis and central nervous system depressant activity of 2-(fluoromethyl)-3-aryl-4(3H)-quinazolinone derivatives.

Some 2-(fluoromethyl) analogues of 2-methyl-3-aryl-4-(3H)-quinazolinones have been synthesized and screened for CNS activities. It was shown that the 2-(fluoromethyl) analogues possess in general more potent CNS depressant activities and less toxicities than their parent compounds. Of particular interest were the 2-(fluoromethyl) analogues (22, 24, and 31) of methaqualone and 6-aminomethaqualone. Compound 24 was more potent in CNS depressant activity and less toxic than methaqualone. Compound 31 exhbited potent central muscle relaxing activity and markedly reduced toxicity as compared with 6-aminomethaqualone.

Animals↗
PubMed1976

[Biological fate of 3H-labeled penfluridol. (3) Correlation between concentration of 3H-penfluridol in the brain and its anti-methamphetamine activity].

The Penfluridol (PFL) is a potent and long-acting neuroleptic belonging to the diphenylbutyl piperidine series. The purpose of the present study is to investigate a correlation between the brain concentration of unchanged 3H-PFL and its neuroleptic activity in the methamphetamine-antagonism test. The experimental animal comprised adult male Wistar rats weighing about 200 g. All the rats were administered 3H-PFL orally and killed at appropriate times after administration. After killing blood samples were collected and the brain and liver were excised. The blood was extracted with 4 volumes of ethanol. The brain and the liver were homogenized in 9 volumes of ethanol. The amount of 3H-PFL in the ethanol extract was determined by thin-layer chromatography. The result showed that the drug level in the brain was relatively constant when the dose was the median effective dose (ED50) for the test at those time intervals after administration.

Animals↗