Biomedical subjects

J Tamaoki

Publications and source records attributed to J Tamaoki.

At least 127 records · Page 7Linked to original sources

PubMed1994

Erythromycin inhibits cholinergic neuro-effector transmission in canine airway smooth muscle.

To elucidate whether macrolide antibiotics affect cholinergic neuro-effector transmission in the airway, we studied canine isolated bronchial segments under isometric conditions in vitro. Addition of erythromycin (3 x 10(-4) M) attenuated the contractile responses to electrical field stimulation (EFS), so that the stimulus frequency required to produce a half-maximal contraction (ES50) increased from 1.3 +/- 0.3 to 5.1 +/- 0.5 Hz (p < 0.001). This effect was concentration-dependent and not influenced by propranolol, indomethacin, ouabain or mechanical removal of the epithelium. In contrast, contractile responses to acetylcholine were not altered by erythromycin. These results suggest that erythromycin may inhibit neuro-effector transmission in the airway cholinergic motor pathway, probably involving the reduction of exocytotic release of acetylcholine from the nerve terminals.

Acetylcholine↗

PubMed1994

[Modulation of cholinergic neurotransmission by Ca(2+)-activated K channel and Na(+)-K(+)-ATPase in canine airway smooth muscle].

Stimulation of Ca(2+)-activated K+ channel and Na(+)-K(+)-ATPase may play an important role in the relaxant responses of airway smooth muscle to certain bronchodilators. To elucidate whether cholinergic neuroeffector transmission can be modulated by Ca(2+)-activated K+ channel and Na(+)-K(+)-ATPase, we studied canine airway smooth muscle under isometric conditions in vitro. Addition of charybdotoxin (ChTx, 10(-7) M) did not alter the contractile responses to acetylcholine (ACh) but augmented electrical field stimulation (FES)-induced contractions at 1-10 Hz (p < 0.01), whereas apamin and glibenclamide were without effect. This effect was dose-dependent, with the maximal increase being 36.8 +/- 5.3% (p < 0.001). Ouabain at a concentration insufficient to alter the resting tension (10(-7) M) increased contractions induced by both EFS and ACh. The magnitude of the increase in contractile responses to EFS was similar to those to ACh at ouabain concentration of up to 3 x 10(-7) M, but the former was significantly greater at 10(-6) M ouabain (p < 0.05). These results suggest that each Ca(2+)-activated K+ channel and Na(+)-K(+)-ATPase may a modulatory role in the cholinergic neurotransmission by inhibiting the exocytotic ACh release from the vagal nerve terminals.

Acetylcholine↗

PubMed1993

Stimulation of ciliary motility mediated by atypical beta-adrenoceptor in canine bronchial epithelium.

The effects of catecholamines on ciliary motility of canine bronchial epithelium was studied by a photoelectric method in vitro. Addition of beta-adrenoceptor agonists increased ciliary beat frequency, a rank order of potency being salbutamol > or = BRL 37344, a selective beta 3-adrenoceptor agonist > norepinephrine. The response to BRL 37344 was relatively resistant to the blockade of beta 1- and beta 2-adrenoceptors but was competitively antagonized by the beta 3-adrenoceptor antagonist cyanopindolol, with the pA2 value being lower than that when salbutamol was used as an agonist. These results suggest that beta 3-adrenoceptors exist in canine bronchial epithelium and that stimulation of this receptor subtype may enhance ciliary motility and, hence, mucociliary transport in the airway.

Adrenergic beta-Agonists↗

PubMed1993

Relaxation and inhibition of contractile response to electrical field stimulation by Beraprost sodium in canine airway smooth muscle.

To elucidate the effect of Beraprost, a stable prostaglandin (PG) I2 analogue, on airway smooth muscle functions and its mechanism of action, we studied canine bronchial segments under isometric conditions in vitro. Addition of PGI2 and its analogues dose-dependently relaxed bronchial smooth muscle precontracted with acetylcholine, with the rank order of potency being Beraprost (1) > or = Hoprost (0.65) > PGI2 (0.04), accompanied by the corresponding increase in intracellular cyclic AMP levels. The Beraprost- and PGI2-induced muscle relaxations were significantly inhibited by each of the PG antagonist diphloretin phosphate, the adenylate cyclase inhibitor SQ 22,536, and the Na(+)-K(+)-ATPase inhibitor ouabain. Beraprost and PGI2 at concentrations insufficient to cause muscle relaxation reduced the contractile responses to electrical field stimulation, whereas they were without effect on those to exogenous acetylcholine. These results suggest that Beraprost not only potently relaxes airway smooth muscle through cyclic AMP production and the subsequent stimulation of Na(+)-K(+)-ATPase but also reduces neurally mediated contraction by inhibiting the release of acetylcholine from the cholinergic nerve terminals.

Acetylcholine↗

PubMed1993

Effect of macrolide antibiotics on ciliary motility in rabbit airway epithelium in-vitro.

We have studied ciliary beat frequency (CBF) of rabbit cultured tracheal epithelium by a photoelectric method in-vitro. Addition of erythromycin and roxithromycin increased CBF in a dose-dependent fashion, whereas clarithromycin was without effect. The rank order potency of macrolide was roxithromycin > erythromycin >> clarithromycin. The roxithromycin-induced increase in CBF was not altered by propranolol, AA-861, or verapamil, but partially attenuated by indomethacin. Roxithromycin increased intracellular cAMP concentrations. These results suggest that certain macrolides can stimulate airway ciliary motility probably via prostaglandin- and cAMP-dependent regulatory pathways, which may affect mucociliary transport function in the respiratory tract.

Animals↗

PubMed1993

Effect of azelastine on sulphur dioxide induced impairment of ciliary motility in airway epithelium.

OBJECTIVE: The effect of azelastine on airway mucociliary transport function was studied by measuring ciliary motility of human bronchial epithelium in vitro with a photoelectric method. METHOD: Bronchial epithelial cells were obtained by fibreoptic bronchoscopy, mounted in a Rose chamber, and perfused with Krebs-Henseleit solution. The preparations were placed on a microscope stage equipped with an illuminator, and the variations of light intensity caused by ciliary beating were detected by a photometer. RESULTS: The addition of azelastine to the perfusate increased ciliary beat frequency (CBF) in a dose dependent manner without ciliary discoordination. The mean (SE) maximal increase from the baseline value and the concentration required to produce a half maximal effect were 27.0 (4.2)% and 9.2 x 10(-6) mol/l, respectively. Exposure of the cells to the perfusate containing 3 ppm sulphur dioxide rapidly decreased CBF by 59.2 (5.0)%, and was accompanied by a reduction in intracellular cyclic AMP levels from 38.1 (4.3) to 10.1 (2.4) pmol/mg protein. This effect was prevented by pretreatment of cells with azelastine in a dose dependent manner. CONCLUSIONS: Azelastine not only stimulates ciliary motility of airway epithelium and hence mucociliary transport function, but may also protect against sulphur dioxide induced ciliary dysfunction, probably by inhibiting intracellular cyclic AMP loss.

Bronchi↗

PubMed1993

Atypical beta-adrenoceptor- (beta 3-adrenoceptor) mediated relaxation of canine isolated bronchial smooth muscle.

To determine whether atypical beta-adrenoceptors (beta 3-adrenoceptors) exist in the airway smooth muscle, we studied isolated bronchial segments from dogs under isometric conditions in vitro. Addition of beta-adrenoceptor agonists produced a concentration-dependent relaxation of tissues precontracted with 10(-5) M acetylcholine, rank-order potency being isoproterenol (1) > or = salbutamol (0.95) > or = BRL 37344, a beta 3-selective adrenoceptor agonist (0.83) > norepinephrine (0.10). Under the condition that alpha- and beta 1-adrenoceptors had been blocked, the relaxant response to salbutamol was competitively antagonized by the beta 2-adrenoceptor antagonist ICI 118551 and the pA2 was 7.01 +/- 0.25 (SE), whereas the response to BRL 37344 was resistant, with an apparent pA2 of 5.66. However, cyanopindolol, an antagonist for atypical beta-adrenoceptors, antagonized the BRL-induced relaxation in a competitive manner, with a pA2 of 6.74 +/- 0.11. This pA2 was lower than that when salbutamol was used as an agonist (P < 0.05). Intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels were increased by BRL 37344 in a concentration-dependent fashion. These results suggest that beta 3-adrenoceptors may exist in canine bronchial smooth muscle and that the stimulation of this type of receptor causes a bronchodilation through a cAMP-dependent pathway.

Acetylcholine↗

PubMed1993

Potentiation of beta-adrenergic function by saiboku-to and bakumondo-to in canine bronchial smooth muscle.

To determine the effects of the Kampo drugs Saiboku-to, Bakumondo-to and Orengedoku-to on beta-adrenergic function in airway smooth muscle, we studied isolated canine bronchial segments under isometric conditions in vitro. Incubation of tissues with these drugs did not alter the contractile responses to acetylcholine and histamine. The relaxation of tissues precontracted with acetylcholine induced by isoproterenol was augmented by Saiboku-to and Bakumondo-to, so that the concentration of isoproterenol required to produce a half-maximal effect (IC50) was decreased from 4.6 +/- 0.5 x 10(-8) M to 1.9 +/- 1.0 x 10(-8) M (P < 0.05) and to 1.0 +/- 0.8 x 10(-8) M (P < 0.01), respectively, whereas Orengedoku-to had no effect. These effects were concentration-dependent with the threshold concentrations being 0.3 mg/ml for Saiboku-to and 0.1 mg/ml for Bakumondo-to. Saiboku-to and Bakumondo-to did not affect cyclic AMP levels in airway smooth muscle per se but potentiated the isoproterenol-induced cyclic AMP accumulation. These results suggest that Saiboku-to and Bakumondo-to but not Orengedoku-to potentiate beta-adrenergic function in airway smooth muscle, which may reflect the efficacy of these drugs on airway hyperresponsiveness and asthma.

Adrenergic beta-Agonists↗

PubMed1993

[Stimulation of ciliary motility by beta 3-adrenoceptor agonist rabbit tracheal epithelium].

To determine whether atypical beta-adrenoceptor (beta 3-adrenoceptor) agonist, BRL 37344, stimulates airway ciliary motility and, if so, what its mechanism of action is, we studied rabbit tracheal epithelium in vitro. Epithelial cells cultured for 7 days were mounted in the Rose chamber and ciliary beat frequency (CBF) was measured by a photoelectric method. Addition of BRL 37344 rapidly increased CBF from 15.5 +/- 0.6 to 20.3 +/- 1.4 Hz (mean +/- SE, p < 0.01), which remained elevated for at least 20 min. This effect was concentration-dependent, the maximal increase from the baseline value and the EC50 being 27.2 +/- 0.4% (mean +/- SE, p < 0.01) and 1.75 x 10(-7) M, respectively. Other beta-adrenoceptor agonists likewise increased CBF, where the rank order of potency was salbutamol (1) > BRL 37344 (0.57) >> norepinephrine (1.3 x 10(-3)). Preincubation of cells with propranolol inhibited the increase in CBF produced by salbutamol, and BRL 37344 significantly raised intracellular cyclic AMP contents. These results suggest that beta 3-adrenoceptor probably exists in rabbit tracheal epithelium and that stimulation of this type of receptor increases ciliary motility through a cyclic AMP-dependent mechanism, an effect that might be of value in enhancing mucociliary transport function in the airway.

Adrenergic beta-Agonists↗

PubMed1993

Effect of somatostatin on contractile and relaxant responses of tracheal smooth muscle in rabbits.

To determine the effect of somatostatin (SRIF) on airway smooth muscle contractile and relaxant responses and its mechanism of action, we studied rabbit tracheal smooth muscle under isometric conditions in vitro. SRIF did not change the contractile responses to electrical field stimulation and acetylcholine, but it inhibited the relaxant responses to isoproterenol in a concentration-dependent manner, an effect that was reversed by treatment of tissues with pertussis toxin (PTX). In contrast, the forskolin- and verapamil-induced relaxations were not altered by SRIF. SRIF also attenuated the increase in intracellular cyclic AMP levels in response to isoproterenol. These results suggest that SRIF may decrease beta-adrenoceptor-mediated muscle relaxation by acting at the site proximal to cyclic AMP synthesis, especially at PTX-sensitive GTP-binding regulatory protein, Gi, coupled to adenylate cyclase.

Animals↗

PubMed1993

[Contribution of K-channel and Na-K-ATPase to the relaxant responses of canine bronchial smooth muscle to various bronchodilators].

To determine whether activations of K-channel and Na-K-ATPase are involved in the action of bronchodilating agents, we studied the effects of various K-channel blockers and ouabain, a Na-K-ATPase inhibitor, on the relaxant responses of canine airway smooth muscle in vitro. Addition of charybdotoxin (ChTx), a Ca-activated potassium channel blocker, and ouabain had no effect on the responses to verapamil and BRL 38227, but inhibited those to salbutamol, forskolin, DBcAMP, and nitroprusside. Apamin, a low-conductance K-channel blocker, and glibenclamide, an ATP-sensitive K-channel blocker, had no effect on the smooth muscle relaxation induced by any agents. The inhibitory effect of ChTx was predominant when the concentration of bronchodilator was low, whereas the effect of ouabain was observed in the presence of a high concentration of bronchodilator. These results suggest that Ca-activated K-channel and Na-K-ATPase may participate in the relaxation induced by bronchodilators that can raise intracellular cyclic nucleotides, and that the contribution of each component differs under different concentrations of the drugs.

Animals↗

PubMed1993

[Effect of bradykinin on airway epithelial ion transport and its modulation by endogenous peptidases].

To elucidate the effect of bradykinin (BK) on airway epithelial ion transport function and its modulation by endogenous peptidases, we studied the electrical properties of canine cultured tracheal epithelium under short-circuited conditions in vitro. Addition of BK to the mucosal side of Ussing chamber increased short-circuit current (SCC) in a dose-dependent manner, the maximal rise from the baseline value (delta SCC max) and the concentration required to produce a half-maximal effect being 7.1 +/- 0.7 microA/cm2 (p < 0.001) and 3.9 +/- 1.0 x 10(-7) M, respectively. This effect was greatly attenuated by the B2-receptor antagonist (D-Arg, Hyp3, Thi5,8, d-Phe7)-BK but not by the B1-receptor antagonist (Des-Arg9, Leu8)-BK. Blockade of angiotensin converting enzyme and aminopeptidase P by captopril and mercaptoethanol did not alter the BK-induced increase in SCC. On the other hand, phosphoramidon and MERGAPTA, inhibitors of neutral endopeptidase and carboxypeptidase N, respectively, strengthened the effect of BK. These results suggest that BK stimulates airway epithelial electrical properties through the activation of B2-receptor subtype, and that endogenous peptidases including neutral nedopeptidase and carboxypeptidase N may play a modulatory role in this action of BK.

Animals↗

PubMed1993

Role of Na(+)-K(+)-ATPase in airway smooth muscle relaxation by vasoactive intestinal peptide and pituitary adenylate cyclase activating peptide.

To elucidate the effects of vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide (PACAP) on airway smooth muscle function, we studied rabbit isolated tracheal segments under isometric conditions in vitro. Addition of VIP and PACAP dose-dependently relaxed tracheal smooth muscle precontracted with acetylcholine, with the order potency being PACAP (1) > or = VIP (0.78), accompanied by the corresponding increase in intracellular cyclic AMP levels. The VIP- and PACAP-induced muscle relaxations were significantly inhibited by ouabain and K(+)-free medium. Incubation of tissues with VIP reduced the contractile responses to electrical field stimulation, whereas PACAP had no effect. These results suggest that VIP and PACAP may cause bronchodilation through activation of Na(+)-K(+)-ATPase and that VIP but not PACAP inhibits the release of acetylcholine from the cholinergic nerve terminals.

Acetylcholine↗

PubMed1993

[Inhibitory effect on sulfur dioxide on ciliary motility in rabbit tracheal epithelium and its prevention by intracellular cyclic AMP].

To elucidate the role of endogeneous cyclic AMP in the protection against airway mucosal dysfunction induced by air pollutants, we studied the effect of sulfur dioxide (SO2) on ciliary motility in rabbit cultured tracheal epithelium in vitro. Exposure of cells to perfusate bubbled with SO2 rapidly decreased ciliary beat frequency (CBF), as assessed by a photoelectric method, from 971 +/- 12 to 718 +/- 28 beats/min by 3 ppm SO2 and from 963 +/- 22 to 635 +/- 34 beats/min by 10 ppm SO2 (p < 0.001, in each case). This effect was reversed by washing out the SO2-containing medium and was accompanied by a corresponding decrease in intracellular levels of cyclic AMP. Preincubation of the epithelial cells with salbutamol, vasoactive intestinal peptide, prostaglandin E2 or 3-isobutyl-1-methylxanthine increased cyclic AMP levels and inhibited the decreases in both CBF and cyclic AMP in response to the subsequent application of SO2 at 3 ppm, whereas dexamethasone had no effect. These results suggest that SO2 decreases airway ciliary motility through the reduction of intracellular cyclic AMP concentration, and that drugs that increase endogeneous cyclic AMP may prevent the SO2-induced impairment of mucociliary transport in the respiratory tract.

Animals↗

PubMed1992

Effects of angiotensin II and angiotensin III on airway epithelial short-circuit current: involvement of pertussis toxin-sensitive G protein.

The effects of angiotensin II (AII) and angiotensin III (AIII) on bioelectric properties of canine cultured tracheal epithelium were investigated. Both peptides increased the short-circuit current (Isc), an effect that was accompanied by the release of prostaglandin (PG) E2 and was abolished by indomethacin and diphenylamine-2-carboxylate but not by amiloride. The AII action was not altered by amastatin. The increases in Isc induced by AII and AIII were inhibited by pertussis toxin, whereas cholera toxin had no effect. Thus, both peptides may selectively stimulate airway epithelial Cl- secretion through the activation of pertussis toxin-sensitive regulatory G protein and the subsequent generation of PGE2.

Angiotensin II↗

PubMed1992

Angiotensin II potentiates neurally mediated contraction of rabbit airway smooth muscle.

The effect of angiotensin II (AT II) on cholinergic neurotransmission in rabbit tracheal segments was studied under isometric conditions in vitro. AT II concentration-dependently potentiated the contractile response to electrical field stimulation (EFS), and caused a leftward shift of the frequency-response curves for EFS, so that the stimulus frequency required to produce a half-maximal effect (ES50), decreased from 7.0 +/- 0.1 to 3.0 +/- 0.1 Hz (P less than 0.01). In contrast, the contractile response to acetylcholine was not affected. Non-peptide AT II receptor antagonist CV-2961 attenuated the effect of AT II on the EFS-induced contraction. Pretreatment of tissues with thiorphan or phosphoramidon did not alter the action of AT II. Thus, AT II may prejunctionally potentiate the neurally-mediated contraction of airway smooth muscle through activation of AT II receptors on the cholinergic nerve terminals, and this effect may not be modulated by endogenous neutral endopeptidase.

Angiotensin II↗

PubMed1992

Thromboxane A2 mimetic U46619 stimulates ciliary motility of rabbit tracheal epithelial cells.

To elucidate whether thromboxane A2 (TxA2), one of the important arachidonic acid metabolites that may play a role in the development of airway inflammation, affects respiratory ciliary motility and, if so, what the mechanism of action is, we measured ciliary beat frequency (CBF) of rabbit cultured tracheal epithelium in response to U46619, a TxA2 mimetic agonist, by a photoelectric method. Addition of U46619 (10(-5) M) increased CBF from 17.7 +/- 0.7 to 22.8 +/- 1.4 Hz (mean +/- SE, p less than 0.01) within 5 min, which was followed by a decline to the baseline value by 10 min. This effect was concentration-dependent, the maximal increase from the baseline value and the drug concentration required to produce a half-maximal effect (EC50) being 26.9 +/- 4.6% (p less than 0.01) and 3 x 10(-7) M, respectively. The U46619-induced increase in CBF was abolished by SQ29548, and TxA2 receptor antagonist, and inhibited by verapamil, a Ca(2+)-entry blocker, and H-7, a protein kinase C inhibitor. These results suggest that TxA2 stimulates ciliary motility through the activation of airway epithelial TxA2 receptors, and that this effect may be exerted from Ca(2+)-influx and protein kinase C.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1992

Effect of erythromycin on ciliary motility in rabbit airway epithelium in vitro.

The effect of erythromycin on ciliary beat frequency (CBF) of rabbit tracheal epithelium was studied by a microphoto-oscillation technique in vitro. Addition of erythromycin dose-dependently increased CBF, the maximal increase from the baseline value and EC50 being 23.3 +/- 4.5% (P less than 0.001) and 6.8 +/- 0.9 mg/L, respectively. This effect was not influenced by autonomic receptor antagonists, blockers of arachidonic acid metabolism, Ca(2+)-free medium, or inhibition of protein kinase C and protein kinase A activities.

Animals↗