Biomedical subjects

I Takayanagi

Publications and source records attributed to I Takayanagi.

At least 37 records · Page 2Linked to original sources

PubMed1996

Age-related changes in alpha-adrenoceptor-mediated blood pressure in the rat: relationship between the potency for phenylephrine and the maximum number of binding sites.

To study the effects of aging on the blood pressure potency of phenylephrine, 6-, 10- and 40-week-old rats were used. In anesthetized rats, the potency (pD2 value) of phenylephrine on the blood pressure tended to increase with age from 6 to 10 weeks, but significantly decreased thereafter with age from 10 to 40 weeks. Similarly, in pithed rats, the potency of phenylephrine significantly increased, but decreased thereafter. In isolated rat thoracic aorta, the pD2 value of phenylephrine from the contractile responses significantly increased with age from 6 to 10 weeks, but decreased thereafter from 10 to 40 weeks. The change in the potency of phenylephrine on the blood pressure was proportional to the pD2 value of phenylephrine estimated in aortic preparations. The specific binding of [3H]prazosin to single smooth muscle cells of thoracic aorta from different aged rats was saturable. The maximum number of binding sites (Bmax) significantly increased with age from 6 to 10 weeks, but decreased thereafter from 10 to 40 weeks. However, the dissociation constant of [3H]prazosin (Kd) did not alter with age. The changes in the potencies (pD2 values) of phenylephrine on the pressure responses and on the contractile responses were proportional to the logarithm of the maximum number of binding sites. The present study suggests that age-related changes in blood pressure are due to changes in the maximum number of binding sites (receptor density) of alpha 1-adrenoceptors.

Adrenergic alpha-Agonists↗

PubMed1996

Pharmacological characteristics of indoline derivatives in muscarinic receptor subtypes.

The present study was designed to investigate which muscarinic receptors the indoline derivatives interact with and also their pharmacological properties. Compounds I and II contracted guinea-pig ileum in a concentration-dependent manner, whereas compounds III-IX behaved as antagonists and Schild plots gave straight lines. 4-DAMP antagonized the contractile responses to compounds I and II, and the pA2 values for 4-DAMP were 8.96 +/- 0.23 and 9.09 +/- 0.06, respectively. In guinea-pig left atrium, compound I partly inhibited twitch responses, whereas compound II did not have any effect. In rabbit vas deferens, compounds I and II produced inhibitory effects on twitch responses evoked by field stimulation. Pirenzepine antagonized the inhibitory responses of compounds I and II, and the pA2 values for pirenzepine were 7.90 +/- 0.13 and 8.12 +/- 0.06, respectively. Compound I has about 150-fold higher affinity to M1 receptors than to M3 receptors, while compound II has about 360-fold higher affinity to M1 receptors. Our results indicate that compounds I and II show 7- and 16-fold higher M1 receptor selectivity than McN-A-343, respectively. Therefore, compound II is selective for M1 receptors over M2 or M3 receptors.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗

PubMed1996

Relaxant responses by optical isomers of ephedrine and methylephedrine in guinea pig tracheal smooth muscle.

The effects of optical isomers of ephedrine and methylephedrine on the guinea pig tracheal smooth muscle were studied. l-Ephedrine markedly caused a graded relaxation of the guinea pig trachea where the tone had been raised spontaneously. A rightward shift of the l-ephedrine concentration-response curve was observed for propranolol and butoxamine, and the pA2 values for propranolol and butoxamine were 8.55 and 6.38, respectively. d-Methylephedrine markedly caused a graded relaxation of the guinea pig trachea contracted with histamine. Propranolol and bupranolol did not affect the relaxant response to d-methylephedrine. d-Methylephedrine competitively antagonized the contractile responses to histamine, and the pA2 value for d-methylephedrine was 5.12. These results suggest that l-ephedrine-induced relaxation of the guinea pig trachea is mediated through beta 2-adrenoceptors, whereas d-methylephedrine relaxes the guinea pig trachea by blocking histamine receptors.

Animals↗

PubMed1996

[Pharmacological studies on drug receptor mechanisms].

During the past ten years, the experiments based on the following three main propositions were carried out in our laboratory. (1) Drug receptor mechanisms. M3-Cholinoceptors and alpha 1-adrenoceptors could be divided into two subtypes which were discriminated by beta-chloroethylamines only in the presence of GTP. The full agonists interacted with both subtypes to induce responses. The partial agonists activated one of them to induce responses but behaved as competitive antagonists when they interacted with the other. The responses mediated through the receptors which were activated by the partial agonists were resistant to myosin light chain kinase inhibitors, while the responses by the activation of the other receptors were suppressed by the inhibitors. The possible mechanisms for responses mediated through alpha 1-adrenoceptors and M3-cholinoceptors were discussed. beta-Adrenoceptors had also two binding sites, high and low affinity sites, which could be discriminated by the partial agonists. (2) Effects of ageing on drug receptor mechanisms. Potencies of alpha- and beta-adrenoceptor agonists increased from the young stage to the adult stage and decreased slowly thereafter to the old stage. The affinities of adrenergic drugs for their receptors did not alter with ageing. The changes in the adrenoceptor-mechanisms with ageing were mainly due to the changes in the amount of receptors. However, the decrease in the potency of beta-agonists in the preparations from the older animals was due to the change in the post beta-receptor processes in responsiveness. No age-related change was observed in serotonin, acetylcholine and tachykinin receptor mechanisms. However, the potencies of acetlcholine and tachykinin were modified by the change in the activity of related enzymes, which altered with ageing. (3) Drug design. Taking into account pharmacological studies on opioid receptors, N-cyclopropylmethyl normorphine derivatives were synthesized. They had more potent analgesic action than morphine through the activation of kappa-opioid receptors. They might not possess dependence liability.

Aging↗

PubMed1996

Phenoxybenzamine discriminates between two distinct populations of histamine H1-receptors in longitudinal muscle of guinea-pig ileum.

The longitudinal muscle of guinea-pig ileum was used as a test tissue. Progressive (up to 70 min) treatment with phenoxybenzamine (10(-6) M) inhibited progressively the response to histamine and progressively decreased the density of histamine H1-receptors. However, the 90 min treatment has no further significant inhibitory effect on the contractile response and did not decrease the density of the receptors. These results suggest that phenoxybenzamine discriminates between two distinct populations of H1-receptors. Furthermore, it was found that the presence of GTP gamma-S made some populations of H1-receptors resistant to phenoxybenzamine and facilitated an interaction of mepyramine with H1-receptors.

Animals↗

PubMed1996

Differentiation of binding sites of CGP12177, a beta 3-adrenoceptor partial agonist, and carteolol, a beta 1/beta 2-adrenoceptor partial agonist, to the beta-adrenoceptors in guinea-pig taenia caecum.

Differentiation of binding sites of CGP12177 and carteolol to the beta-adrenoceptors in the guinea-pig taenia caecum was investigated. Carteolol and CGP12177 competitively antagonized the relaxation responses to isoprenaline, and the pA2 values were 9.87 and 9.33, respectively. Butoxamine, a beta 2-selective antagonist, caused competitive antagonism of the relaxant responses to carteolol, and the pA2 value for butoxamine was 6.22. However, butoxamine (10(-4) M) did not significantly affect the relaxant responses to CGP12177. CGP12177 caused competitive antagonism of the relaxant responses to carteolol, and the pA2 value for CGP12177 was 9.32. However, carteolol (10(-6) M) did not significantly affect the relaxant responses to CGP12177. The competitive inhibition curve for specific binding of 50 nM [3H]befunolol by carteolol showed a biphasic shape, although the curve by CGP12177 was monophasic. Moreover, the competitive inhibition curve for specific binding of 100 nM [3H]CGP12177 by CGP12177 showed a biphasic shape, although the curve by carteolol indicated partial inhibition. These results suggest that the low affinity site of beta-adrenoceptor and beta 3-adrenoceptors are different from each other.

Adrenergic beta-Agonists↗

PubMed1995

Involvement of botulinum C3-sensitive GTP-binding proteins in alpha 1-adrenoceptor subtypes mediating Ca(2+)-sensitization.

The mechanisms of alpha 1-adrenoceptor agonist-mediated sensitization of the contractile apparatus of smooth muscle to Ca2+ were studied in beta-escin-permeabilized thoracic arterial smooth muscle of rabbit. Addition of norepinephrine (10 microM) plus guanosine 5'-triphosphate (GTP, 50 microM) significantly enhanced Ca2+ sensitivity as compared with the addition of 0.3 microM Ca2+ alone (pCa6.5). In beta-escin-skinned smooth muscle of chloroethylclonidine-treated tissues, the enhancement of Ca(2+)-contraction produced by norepinephrine or clonidine was completely inhibited by guanosine 5'-O-(beta-thiodiphosphate) (GDP beta-S, 1 mM). In addition, Clostridium botulinum C3, which inactivates low molecular weight GTP-binding protein families, abolished norepinephrine- or clonidine-induced Ca(2+)-sensitization, but did not affect clonidine-induced translocation of protein kinase C to the membrane. The norepinephrine-enhanced Ca2+ sensitivity was partially reversed by a pretreatment with a selective myosin light chain kinase inhibitor (8R*, 9S*, 11S*)-(-)-9-hydroxy-9-methoxycarbonyl-8-methyl-14-n- propoxy-2,3,9,10-tetrahydro-8,11-epoxy,1H,8H,11H-2,7b,11a- triazadibenzo[a,g]cycloocta[cde]trinden-1-one (KT5926, 500 nM), but those of clonidine and in the chloroethylclonidine-treated tissues norepinephrine were not. These results suggest that Ca(2+)-sensitization produced by the activation of the alpha 1-adrenoceptor subtypes is linked via a low molecular weight GTP-binding protein (Rho), and the regulations of phosphorylation in contractile elements.

ADP Ribose Transferases↗

PubMed1995

Possible mechanisms of beta-adrenoceptor-mediated relaxation induced by noradrenaline in guinea pig taenia caecum.

The mechanisms of the beta-adrenoceptor-mediated relaxation induced by noradrenaline in guinea pig taenia caecum were investigated. Noradrenaline caused graded relaxation of this preparation. However, the concentration-response curves for noradrenaline were unaffected by propranolol (approximately 10(-5) M) or phentolamine (approximately 10(-5) M). The responses to noradrenaline were antagonized in a concentration-dependent manner by bupranolol, and Schild plots of the data revealed a pA2 value of 5.53. Also, bupranolol antagonized responses to isoprenaline, and Schild plots of the data revealed the pA2 value to be 8.53. Noradrenaline significantly increased the cyclic AMP level in this preparation. Bupranolol (10(-4) M) significantly decreased the cyclic AMP response elicited by noradrenaline, whereas propranolol (10(-5) M) produced no effect. These results suggest that the relaxant response to noradrenaline in guinea pig taenia caecum is mainly mediated by beta 3-adrenoceptors (or atypical beta-adrenoceptors) and that in guinea pig taenia caecum noradrenaline behaves as a beta 3-selective adrenoceptor agonist.

Adrenergic beta-Agonists↗

PubMed1995

Alpha 1A-adrenoceptor subtype effectively increases Ca(2+)-sensitivity for contraction in rabbit thoracic aorta.

1. Norepinephrine and phenylephrine increase cytosolic Ca2+ concentration ([Ca2+]i) and muscle tension, which shows positive correlation between [Ca2+]i and tension development. 2. The slopes of regression lines between [Ca2+]i and tension development for norepinephrine and phenylephrine in tissues treated with an irreversible alpha 1B-adrenoceptor selective blocking agent, 10(-4) M chloroethylclonidine, were significantly steeper than those with untreated tissues. 3. Myosin light chain kinase inhibitors, KT5926 (3 x 10(-6) M) and K252a (10(-6) M) more selectively reduced the contraction produced by norepinephrine (3 x 10(-7) M) than that produced by clonidine (3 x 10(-6) M). 4. In the chloroethylclonidine-treated tissues, KT5926 and K252a did not tend to affect the contraction induced by norepinephrine and clonidine. 5. These results suggest that the contractile response through the alpha 1A-adrenoceptor subtype causes a greater muscle tension than that through the alpha 1B-subtype at the same level of [Ca2+]i, and that the alpha 1A-adrenoceptor subtype mainly activates myosin light chain kinase independent pathways of contractile mechanisms in vascular smooth muscle of rabbit.

Adrenergic alpha-Agonists↗

PubMed1995

Effect of omega-conotoxin GVIA on tetrodotoxin-insensitive acetylcholine release by nicotine in guinea-pig bladder.

1. Contractile responses and acetylcholine release evoked by nicotine and electrical field stimulation (EFS) were determined by isotonic transducer and radioimmunoassay, respectively. 2. Nicotine-induced contraction was reduced to 30% by nicotinic receptor antagonist, hexamethonium but was insensitive to tetrodotoxin. EFS-induced contraction was abolished by tetrodotoxin but was insensitive to hexamethonium. Replacement of external Na by choline completely abolished the contractile responses evoked by nicotine and EFS. 3. Both contractions evoked by nicotine and EFS were inhibited by omega-conotoxin GVIA, and inhibitory effects of the toxin were greater in low Ca concentrations. 4. In the condition that external Na or Ca is omitted from physiological solution, acetylcholine release evoked by nicotine was not observed. Nicotine-induced acetylcholine release was partially inhibited by omega-conotoxin but was insensitive to tetrodotoxin. 5. In conclusion, nicotine interacts with nicotinic receptors located on nerve terminals and produces transmitter release which depends on external Na through tetrodotoxin-insensitive mechanisms. It is suggested that voltage-dependent omega-conotoxin sensitive Ca channels are partially involved in the nicotine-induced transmitter release.

Acetylcholine↗

PubMed1995

Inhibitory effects of d-nicotine on the responses evoked by 1-isomer in trachea and bronchus isolated from guinea-pig and rabbit.

1. The effects of d-nicotine on the responses induced by 1-isomer were studied in tracheae and bronchi isolated from guinea-pigs and rabbits. In guinea-pigs trachea 1-nicotine produced a biphasic response consisting of initial contraction and following relaxation. In other airway preparations 1-nicotine produced only contraction. 2. d-Nicotine did not produce any responses except for the case of guinea-pig trachea. d-isomer produced only relaxation and relative potency was approximately 0.44 in guinea-pig trachea. 3. Pretreatment with d-nicotine (30-300 microM) reduced concentration response curves for 1-isomer in a non-competitive manner in all preparations used in this study. 4. 1-nicotine at the concentration of 3 microns, which did not produce any response itself, reduced the concentration response curve of 1-nicotine in guinea-pig trachea. 5. Inhibition by d-nicotine or 1-nicotine (3 microM) of the concentration-response curve of 1-nicotine may be due to desensitization of nicotine receptors.

Animals↗

PubMed1995

Effects of acute and short-term repeated application of fullerene C60 on agonist-induced responses in various tissues of guinea pig and rat.

1. Effects of fullerene C60 in trachea, right atria, ileum and stomach (fundus) of guinea pig and vas deferens and uterus of rat were studied pharmacologically. 2. C60 (4 microM) had no direct effect in all tissues. In guinea pig trachea and heart, relaxation and positive inotropic and chronotropic actions of isoprenaline and in isolated rat vas deferens and uterus the responses on norepinephrine and oxytocin were not affected by the short-term repeated application of C60 30 mg/kg i.p. for 4 wk. 3. The pD2 values (potencies) of acetylcholine in ileum and its longitudinal muscle from guinea pig after the short-term repeated application of C60 were significantly smaller than those obtained without the application. The value of 5-hydroxytryptamine in rat stomach (fundus) also tended to be smaller than obtained without the application. 4. Atropine inhibited competitively the contractions for acetylcholine in the longitudinal muscles prepared from C60-treated and non-treated guinea pigs, and the pA2 values for atropine were not significantly different with each other. 5. These results suggest that C60 has no direct effects or antagonistic properties toward drug receptors, but sub-chronic exposure of C60 decreased responsiveness. This may be due to a change in post-receptor processes.

Acetylcholine↗

PubMed1995

Effect of bupranolol on CGP 12177-induced relaxation and cAMP accumulation in the guinea pig taenia caecum.

1. The effect of bupranolol on CGP 12177-induced relaxation and cAMP accumulation in the guinea pig taenia caecum was examined. 2. The relaxant response to CGP 12177 was unaffected by propranolol (approximately 10(-6) M), whereas that to CGP 12177 was antagonized in a concentration-dependent manner by bupranolol; Schild plot of the data revealed the pA2 value of 5.61. 3. CGP 12177 significantly increased cyclic AMP level in this preparation. Bupranolol (10(-4) M) significantly decreased the cyclic AMP level that was elicited by CGP 12177, whereas propranolol (10(-5) M) produced no effect. 4. These results suggest that bupranolol appears to be an efficient beta3-antagonist in the guinea pig taenia caecum and confirm that the response to CGP 12177 is mediated by beta3-adrenoceptors.

Adrenergic beta-Antagonists↗

PubMed1995

High-performance liquid chromatography of fullerence (C60) in plasma using ultraviolet and mass spectrometric detection.

Fullerence (C60) was determined by high-performance liquid chromatography using both ultraviolet and mass spectrometric detection. The detection limit for each method was 0.05 and 2.0 ng (signal-to-noise ratio (S/N = 2)) per injection, respectively. Rat plasma spiked with C60 (10 micrograms/ml) was extracted using solid phase extraction with a recovery of 62.1% and the coefficient of variation (c.v., n = 5) between intra-day assays was 4.0%. The calibration curve for peak area and plasma C60 concentration with ultraviolet detection showed good linearity (r = 0.996) over the range 0.5-60 micrograms/ml. This newly developed method was applied to rat plasma samples after intravenous administration of C60 solubilized with polyvinylpyrrolidone.

Animals↗

PubMed1995

Signal transduction pathway involved in beta 3-adrenoceptor-mediated relaxation in guinea pig taenia caecum.

Experiments were carried out to examine the components of the intracellular second messenger system that is involved in beta 3-adrenoceptor (atypical beta-adrenoceptors)-mediated relaxation in the guinea pig taenia caecum. Propranolol and butoxamine caused competitive antagonism of the relaxant response to isoprenaline. However, propranolol or butoxamine did not significantly affect the relaxant responses to CGP 12177 (4-[3-[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2H- benzimidazol-2-one), a beta 3-adrenoceptor agonist. The concentration-response curves of the isoprenaline-induced increase in adenosine 3',5'-cyclic monophosphate (cyclic AMP) levels were shifted to the right in a parallel manner by propranolol and butoxamine. However, propranolol or butoxamine did not significantly affect the concentration-response curve for the CGP 12177-induced increase in cyclic AMP levels. MDL 12330 (cis-N-(2-phenylcyclopentyl)-azacyclotridec-1-en-2-amine) inhibited the isoprenaline- or CGP 12177-induced increase in cyclic AMP levels. These results suggest that the production of cyclic AMP contributes to the beta 3-adrenoceptor (or atypical beta-adrenoceptor)-mediated relaxation of the guinea pig taenia caecum.

Adenylyl Cyclases↗

PubMed1994

Alpha 1-adrenoceptor subtypes mediating the regulation and modulation of Ca2+ sensitization in rabbit thoracic aorta.

Norepinephrine (10 microM), methoxamine (100 microM) and clonidine (100 microM) with guanosine 5'-triphosphate (GTP, 50 microM) or guanosine 5'-O-(3-thiotriphosphate) (GTP gamma-S, 10 microM) all significantly enhanced the contraction induced by 0.3 microM Ca2+ (pCa6.5) in beta-escin-skinned smooth muscle of rabbit thoracic aorta. The enhancement of Ca2+ contraction produced by norepinephrine was greater than that produced by methoxamine or clonidine. In beta-escin-skinned strips of chloroethylclonidine-pretreated smooth muscle, the enhancement of Ca2+ contraction produced by norepinephrine was significantly decreased, whereas the amplitude was the same as that produced by methoxamine or clonidine; this enhancement was inhibited by the selective alpha 1A-adrenoceptor antagonist WB 4101 (100 nM). The enhancement of Ca2+ contraction produced by methoxamine and clonidine was not affected by chloroethylclonidine pretreatment. The effects of methoxamine, clonidine and norepinephrine in the chloroethylclonidine-pretreated tissue were all inhibited by guanosine 5'-O-(2-thiodiphosphate) (GDP beta-S, 1 mM) and 1-(5-isoquinolinylsulfonyl)-methylpiperazine (H-7, 20 microM). Furthermore, the phosphorylation of myosin light chain produced by norepinephrine was greater than that produced by clonidine. These results suggest that both alpha 1-adrenoceptor subtypes (alpha 1A and alpha 1B) increase the Ca2+ sensitivity of contractile elements, and that the Ca2+ sensitization produced by alpha 1A-subtype receptors is mediated through G-protein and protein kinase C, and plays an important role in contraction of smooth muscle of rabbit thoracic aorta.

Animals↗

PubMed1994

Pre- and postjunctional actions of endothelin in the rat iris sphincter preparation.

Effects of endothelins (ETs) were studied in the rat iris sphincter preparation. Three peptides (ET-1, ET-2 and ET-3) caused contractile responses, and the rank order of agonist potency was: ET-1 = ET-2 > ET-3. The concentration-response curve to ET-1 was shifted to the right by the ETA receptor antagonist cyclo [D-Asp-L-Pro-D-Val-L-Leu-D-Trp] (BQ-123: 10(-7) M), the pA2 value of which was 7.41 +/- 0.09 (n = 4). ET-1 and ET-3, at the concentration of 10(-9) M, potentiated cholinergic contractions evoked by electrical field stimulation (5 and 20 Hz) without affecting the postjunctional sensitivity to carbachol. This potentiating effect was not influenced by BQ-123 (10(-6) M). The ET-evoked percentage increase in the stimulation-induced contraction observed at 5 Hz was significantly greater than that at 20 Hz. A release of immunoreactive ET was detected when the preparation was stimulated at 20 Hz (1.81 +/- 0.36 pg/sphincter n = 6). ET release evoked by 20 Hz stimulation was completely abolished by tetrodotoxin (10(-7) M). In conclusion, ET interacts with two different receptor types, ETA and non-ETA receptors (probably ETB) which exist post- and presynaptically at cholinergic neuroeffector junctions of the rat iris preparation. Stimulation of ETA receptor results in a direct muscle contraction and non-ETA receptor activation facilitates the acetylcholine output from cholinergic nerve endings. It is suggested that ET released from a tetrodotoxin-sensitive site is involved in the modulation of acetylcholine release in the rat iris sphincter preparation.

Amino Acid Sequence↗

PubMed1994

A regional difference of the effect of tachykinin on cholinergic response evoked by electrical field stimulation in the rabbit airway.

1. Experiments were designed to determine whether regional differences exist in the effects of phosphoramidon (a metalloprotease inhibitor) and [D-Arg,1D-Pro,2 D-Trp,7,9Leu,11]-substance P (a tachykinin antagonist: rpwwL-SP) on contractile responses to electrical field stimulation (EFS) in rabbit airways. 2. EFS contractions were potentiated by phosphoramidon and were attenuated by rpwwL-substance P at low frequencies (less than 10 Hz). 3. Potentiating effect of phosphoramidon was more pronounced in distal bronchus than trachea and was proportional to total proteinase activity. 4. The rank order of inhibitory effect of rpwwL-SP was: trachea > proximal bronchus > distal bronchus, and inverse relationship was observed between the drug's inhibitory effect of drug and total proteinase activity in three different regions. 5. Good correlation was observed between total proteinase activity and pD2 value of neurokinin A in each airway region. 6. In conclusion, tachykinin modulates acetylcholine release in the contractile response to EFS at low frequencies (less than 10 Hz), and regional differences in the effects of the inhibitor and the antagonist on EFS-evoked contractions in the rabbit airway were suggested to be due to heterogenous distribution of the metalloprotease which metabolized tachykinins.

Acetylcholine↗