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Biomedical subjects

H Tsuchihashi

Publications and source records attributed to H Tsuchihashi.

At least 55 records · Page 3Linked to original sources
PubMed1991

MCI-9042: high affinity for serotonergic receptors as assessed by radioligand binding assay.

This study assessed the specificity of displacement potencies of MCI-9042 [+/-)-1-[o-[2-(m-methoxyphenyl)ethyl]phenoxy]-3-(dimethylamino)- 2-propyl hydrogen succinate hydrochloride), a new antiplatelet agent, in [3H]4-bromo-2,5-dimethoxyphenylisopropylamine [( 3H]DOB) and [3H]ketanserin binding to 5HT2-serotonergic receptors in the rat brain using the radioligand binding method. The assessment of the displacement potencies of MCI-9042 and its derivative, M-1 [(+/-)-1-[2-[2-(3-methoxyphenyl)ethyl]phenoxy]-3-(dimethylamino)- 2-propanol)hydrochloride), on alpha 1-, alpha 2-, beta-adrenergic, 5HT1-, 5HT2- and muscarinic receptors were also studied. MCI-9042 and M-1 showed strong displacement effects to 5HT2-receptors using [3H]DOB binding and [3H]ketanserin binding sites, and weak displacement effects for [3H]serotonin, [3H]prazosin, [3H]p-aminoclonidine, [3H]CGP12177 and [3H]QNB binding to 5HT1-, alpha 1-, alpha 2-, beta-adrenergic receptors and muscarinic receptors. Thus, the present study suggests that MCI-9042 is specific for 5HT2-receptor.

Adrenergic alpha-Agonists↗
PubMed1991

Changes in alpha 1- and beta 1-adrenergic receptors and calcium ion binding sites in the fetal myocardium of spontaneously hypertensive rats (SHR).

The present study examined changes in [3H]prazosin, [125I]iodocyanopindolol and [3H]nitrendipine binding to alpha 1- and beta 1-adrenergic receptors and Ca2+ binding sites of cardiac muscle isolated from fetal Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), using the radioligand binding assay method. The catecholamine concentration in the cardiac muscle of both groups was also determined. The Bmax values in beta 1-adrenoceptors and Ca2+ binding sites in SHR cardiac muscle were lower than those of WKY, but values for SHR alpha 1-adrenoceptors were higher than those of WKY. The Kd values of beta 1-adrenoceptors in cardiac muscles of SHRs were also lower than those of WKY. On the other hand, there were no differences between the catecholamine concentrations in fetal SHR and WKY cardiac muscles. Thus, significant differences in both alpha 1- and beta 1-adrenoceptors and Ca2+ binding sites were already present in fetal SHR hearts, thus suggesting that the changes in fetal hearts of SHRs may be caused by genetic defects in the mother rats at early age.

Animals↗
PubMed1991

Beta-blocking potency and selectivity of bopindolol and its two metabolites for beta 1- and beta 2-adrenergic receptors as assessed by radioligand binding assay.

Using a radioligand binding assay, we assessed the affinity and selectivity of the antagonistic effects of bopindolol (4-(benzoyloxy-3-tert-butylaminopropyl)-2-methylindole hydrogen-malonate) and its two metabolites, (18-502, (4-(3-tert-butylamino-2-hydroxypropoxy)-2-methyl indole) and 20-785, (4-(3-tert-butylaminopropoxy)-2-carboxyl indole], for beta 1- and beta 2-adrenoceptors and on 5HT1B-receptors in rat brain and heart. In addition, we also determined the pA2 values of these agents for their antagonistic effects toward positive chronotropic and inotropic actions (beta 1-adrenoceptors) and for their antagonistic effects toward isolated tracheal relaxation (beta 2-adrenoceptors), using isoproterenol as an agonist. The data showed that bopindolol was more selective for beta 2-adrenoceptors than for beta 1-adrenoceptors and 5HT1B-receptors, but its two metabolites (18-502 and 20-785) did not have significant selectivity for beta 1- and beta 2-adrenoceptors, using both [3H]CGP12177 and [125I]ICYP ([125I]iodocyanopindolol) bindings. In contrast, the results from pharmacological assessment for antagonistic potencies, using atria and trachea, showed that bopindolol and its two metabolites did not have significant selectivity on beta 1- and beta 2-adrenoceptors. A major metabolite of bopindolol, 18-502, had higher pKi and pA2 values for beta-adrenoceptors and 5HT1B-receptors than those of bopindolol and 20-785. These results indicate, first, that a radioligand binding assay for the assessment of the selectivity of bopindolol and its two metabolites for beta 1- and beta 2-adrenoceptors is more effective than pharmacological experiments, and that there is a possibility that its two metabolites also contribute to the strong beta-blocking action of bopindolol.

Adrenergic beta-Antagonists↗
PubMed1991

Binding characteristics of alpha 1-adrenoceptors in bovine prostate using a radioligand binding assay.

Binding characteristics of alpha 1-adrenoceptors in the bovine prostate were examined using a radioligand binding assay. [3H]Bunazosin was used as a radioligand. The optimal incubation conditions for the radioligand binding assay were determined: incubation time (30 min), protein concentration (0.2 mg/tube) and temperature (30 degrees C). Scatchard plots for alpha 1-adrenoceptors in bovine prostates were linear and the Kd and Bmax values were 0.61 nM and 49.8 fmol/mg protein, respectively. The pKi value of terazosin was significantly higher than those of prazosin, bunazosin or phentolamine in the bovine prostate. Since this radioligand binding assay using [3H]bunazosin demonstrated the presence of alpha 1-adrenoceptors in bovine prostates, this method is useful for the assessment of alpha 1-blockers of new chemicals synthesized for the treatment of the benign prostatic hyperplasia.

Adrenergic alpha-Antagonists↗
PubMed1991

Binding characteristics of [3H]ketanserin for serotonin-2 receptor in the rabbit platelet.

The present study was designed to examine 1) the properties of [3H]ketanserin binding to serotonin-2 (5HT2)-serotonergic receptors in the rabbit platelet membranes, 2) displacement affinities of various chemicals and 3) difference of the affinities between their chemicals and new agents, MCI-9042 and M-1. The plots of specific binding obtained from the Scatchard analysis using [3H]ketanserin for the platelet membranes were monophasic when the non-specific binding was determined by the use of 0.1 mM serotonin (5HT), and the Kd and Bmax values were 3.93 +/- 0.41 nM and 1.19 +/- 0.20 pmol/mg protein, respectively. The displacement potencies of chemicals which were serotonin receptor-, dopamine receptor-, histamine receptor-, and alpha-adrenoceptor-related agents were characterized by [3H]ketanserin binding to 5HT2-serotonergic receptor. The pKi values of a new antiplatelet agent, MCI-9042, and its metabolite, M-1, were 7.19 and 7.59, respectively and these values were lower than those of ketanserin and pirenperone but higher than those of methysergide, cinanserin and cyproheptadine. The affinities of ketanserin for 5HT2-receptors in the rabbit platelet were similar to those for 5HT2-receptors previously identified in the rat frontal lobe and in canine aorta, but cinancerin was selective to 5HT2-receptors in the rat frontal lobe and in canine aorta, prazosin was selective to 5HT2-receptor in the rabbit platelet, and MCI-9042 and M-1 had the same affinities to the receptors in the rat frontal lobe and in the rabbit platelet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Comparison of alpha 1-adrenoceptors between rat brain and spleen.

Scatchard analyses of 3H-prazosin binding in rat brain membranes showed biphasic curves, which identified the presence of alpha 1High- and alpha 1Low-affinity sites. The alpha 1High-affinity site was completely inhibited by 0.1 microM phenoxybenzamine. On the other hand, 3H-prazosin binding in rat spleen membranes resulted in linear curves that were identical to the binding curve for the alpha 1High-affinity site in the brain. The displacement potencies of alpha 1-adrenergic antagonists were characterized by 3H-prazosin binding to alpha 1High-affinity sites in the rat spleen and brain and alpha 1Low-affinity sites in the brain in the presence of 0.1 microM of phenoxybenzamine. The affinities of WB-4101, phenoxybenzamine, phentolamine, chlorpromazine, labetalol and nifedipine for brain alpha 1High-affinity sites were significantly higher than those in the spleen. The affinities of most ligands for alpha 1Low-affinity sites were significantly lower than those for both alpha 1High-affinity sites in the brain and spleen, but chlorethylclonidine was significantly selective for alpha 1Low-affinity sites, and bunazosin, dibenamine and 5HT had the same affinities for the alpha 1Low- and both alpha 1High-affinity sites. These results show that two alpha 1-adrenoceptor subtypes, alpha 1High- and alpha 1Low-affinity, are present in the rat brain and that a different alpha 1High-subtype, exists in the rat spleen.

Adrenergic alpha-Antagonists↗
PubMed1990

Screening test of stimulants in human urine utilizing headspace gas chromatography for field test.

An accurate and simple screening method of stimulants in human urine using headspace gas chromatography utilizing heat of dissolution of potassium carbonate was developed. A 4.9-g portion of potassium carbonate was put into the vial prior to sending to the field, and a 5-ml aliquot of urine, suspected of containing stimulants and internal standard components was pipetted. After the vial was sealed and shaken by hand, 1 ml of its headspace gas was taken by disposable syringe and injected into the gas chromatograph. A compact gas chromatograph device with flame ionization detector and fused silica capillary column was developed for this experiment. Detection limits of methamphetamine and amphetamine were 1.0 micrograms/ml and 1.5 micrograms/ml, respectively.

Amphetamine↗
PubMed1990

Characteristics of 125I-iodocyanopindolol binding to beta-adrenergic and serotonin-1B receptors of rat brain: selectivity of beta-adrenergic agents.

The present study was designed to examine the specificity of beta-adrenergic antagonists for beta 1-, beta 2-adrenergic and 5HT1B-serotonergic receptors by the competitive interaction with 125I-iodocyanopindolol (125I-ICYP) as a radioligand. The beta 1-adrenoceptors were preferred by acebutolol, atenolol, betaxolol, practolol, and l-, dl- and d-metoprolol, while butoxamine and lCl-118,551 preferred beta 2-adrenoceptors. The selectivities of these beta 1- and beta 2-antagonists are well-known, but alprenolol which is known as a non-selective antagonist was 7.2-fold more selective for the beta 2-adrenoceptors in the present study. All beta-antagonists used were more selective towards beta-adrenoceptors as compared with 5HT1B-receptors. Good correlations were observed between the potencies of beta-adrenoceptor antagonists for inhibition of 125I-ICYP binding to beta 1- and beta 2-adrenoceptor sites and their potencies for inhibiting the binding of the same radioligand to 5HT1B-serotonergic receptor sites. These results suggest that beta-adrenoceptor antagonists can bind to beta-adrenoceptors and 5HT1B-receptors.

Adrenergic beta-Agonists↗
PubMed1989

Headspace gas chromatography of stimulants in urine by in-column trifluoroacetyl derivatization method.

The analysis of stimulants in urine using a headspace gas chromatography system equipped with an in-column sample trifluoroacetylation unit was investigated. A 5-ml aliquot of urine containing stimulants was pipetted into a 20-ml autosampler vial together with 3.5 g of potassium carbonate. The vial was sealed and heated for 20 min at 80 degrees C, then 0.8 ml of the headspace gas and N-methylbis(trifluoroacetamide) gas were injected simultaneously into the gas chromatograph equipped with a flame ionization detector and a fused-silica capillary column (DB-1, 30 m x 0.32 mm I.D., film thickness 0.25 micron), with a gas-tight syringe. Calibration graphs prepared by the absolute calibration curve method showed good linearity over the concentration range of 0.04 to 50 micrograms/ml for methamphetamine hydrochloride and amphetamine sulphate. The detection limits were 0.03 micrograms/ml for both of these compounds.

Acetamides↗
PubMed1989

Alpha-blocking potencies of antihypertensive agents (prazosin, terazosin, bunazosin, SGB-1534 and ketanserin) having with quinazoline or quinazolinedione as assessed by radioligand binding assay methods in rat brain.

The comparative effects of antihypertensive agents, quinazoline or quinazolinedione residues (prazosin, bunazosin, terazosin, SGB-1534, and ketanserin), on the binding of [3H]prazosin, [3H]p-aminoclonidine and [3H]dihydroalprenolol([3H]DHA) to alpha 1-, alpha 2-, and beta-adrenoceptors in the rat brain were examined using radioligand binding assay methods. pA2 values were also obtained in the isolated rat aorta (alpha 1-adrenoceptor) using phenylephrine as an agonist. A strong inhibition by these drugs of [3H]prazosin binding to alpha 1-adrenoceptors was observed, while the inhibition of [3H]DHA binding to beta-adrenoceptors and [3H]p-aminoclonidine binding to alpha 2-adrenoceptor was found to be very weak. The rank order of antagonistic potencies of these drugs against the alpha 1-adrenergic receptors was determined by inhibition constants (Ki) with SGB-1534 = prazosin = bunazosin greater than terazosin greater than ketanserin. The pA2 value of these drugs, in contrast, had prazosin with higher pA2 value than that of SGB-1534. From these two different types of experiments, it was clear that these drugs antagonized alpha 1-adrenoceptors even in the central nervous system, and the side chains bound to quinazoline and quinazolinedione residues may play an important role in the antagonistic potencies for alpha 1-adrenoceptors in the central nervous system as in the peripheral tissues.

Adrenergic alpha-Antagonists↗
PubMed1989

Three binding sites of 125I-iodocyanopindolol, i.e. beta 1, beta 2-adrenergic and 5HT1B-serotonergic receptors in rat brain determined by the displacement and Scatchard analysis.

The selectivity of binding of 125I-iodocyanopindolol (125I-ICYP) to beta 1-, beta 2-adrenergic and 5HT1B-serotonergic receptors were analysed using both the Scatchard and displacement methods. When the binding of 125I-ICYP to the rat brain membrane was examined by means of the displacement analysis with l-metoprolol, triphasic displacement curves were observed. Analyses carried out on the basis of the displacement of 125I-ICYP by beta-selective antagonists, alpha-adrenergic agonists and antagonists, and serotonergic agonists and antagonists indicated the correspondence of the super high, high- and low-affinity sites of 125I-ICYP binding to beta 2-, beta 1-adrenergic and 5HT1B-receptors, respectively. By contrast, the Scatchard analysis revealed the biphasic character of the 125I-ICYP binding and the complete inhibition of the binding to high- and low-affinity sites by l-metoprolol (30 microM) and 5-hydroxytryptamine (5HT, 10 microM), respectively, suggesting the correspondence of the high- and low-affinity sites to beta-adrenergic and 5HT1B-receptors. Thus, regarding the determination of the selectivity of binding of a radioligand, the displacement analysis is more informative than the Scatchard analysis. In the case of 125I-ICYP the separation of beta 1- and beta 2-adrenergic receptors becomes feasible only with the displacement method.

Animals↗
PubMed1989

Binding characteristics of 3H-CGP12177 to beta-adrenoceptors in rat myocardial membranes.

The present study was designed to examine the selectivity of 3H-CGP-12177 (4-(3-t-butylamino-2-hydroxypropoxy)-[5,7-3H]benzimidazole-2-one hydrochloride) for beta 1- and beta 2-adrenergic receptors by the Scatchard and the displacement analysis. The plots of specific binding obtained from the Scatchard analysis using 3H-CGP12177 for the rat myocardium membrane were uniphasic when the non-specific binding was determined by the use of 10 microM I-propranolol, and the Kd and Bmax values were 408.53 +/- 67.20 pM and 12.27 +/- 0.83 fmoles/mg protein, respectively. On the other hand, two binding sites were observed in the displacement curve when I-metoprolol was used as a competitor. The existence of these two binding sites implied the selectivity of 3H-CGP12177 to beta-adrenoceptors because 3H-CGP12177 was 1.8-fold more selective towards beta 1-adrenoceptors than beta 2-adrenoceptors. In addition, these two binding sites could be regarded as beta 1- and beta 2-adrenergic receptors from the evaluation of the binding characteristics beta-adrenoceptors by the displacement analysis using beta-selective antagonists. Thus, 3H-CGP12177, a hydrophilic radioligand, was useful for the binding assay of beta-adrenoceptors in rat myocardial membranes.

Adrenergic beta-Antagonists↗
PubMed1989

Selectivity of bunitrolol for beta 1- and beta 2-adrenergic receptors and 5HT1B-receptors: assessment by biphasic Scatchard plots and biphasic displacement curve analysis with 125I-iodocyanopindolol and 3H-CGP12177.

The preference by bunitrolol for beta 1- and beta 2-adrenoceptors of the rat brain, heart and/or lung was assessed by the radioligand binding assay method with 125I-iodocyanopindolol (125I-ICYP) or 3H-CGP12177. Scatchard plots of 125I-ICYP binding in the presence of bunitrolol were found to be non-linear. The inhibition constants (Ki) of bunitrolol for high (beta 2-) and low affinity sites (beta 1-) were: 0.42 +/- 0.16 nM for beta 1 and 3.55 +/- 1.61 nM for beta 2 (beta 1 greater than beta 2), respectively. Displacement experiments conducted with the preparations of the rat brain using 125I-ICYP or with the preparations of the rat heart using 3H-CGP12177 yielded Ki values for bunitrolol of 0.53 +/- 0.20 (beta 1) and 2.37 +/- 0.78 (beta 2) nM for 125I-ICYP binding and 2.01 +/- 0.38 (beta 1) and 12.67 +/- 6.54 (beta 2) nM for 3H-CGP12177 binding. In addition, the Ki value for 5HT1B-receptors assessed in displacement experiments conducted with 125I-ICYP in the presence of 30 microM I-metoprolol in the rat brain was 10.54 +/- 5.92 nM. Thus, bunitrolol is a beta 1-selective antagonist.

Adrenergic beta-Antagonists↗