Characteristics of cardiac .BETA.-adrenoceptors in Suncus murinus.

Abe, Kazuho; Wang, Chao-Hsiung; Tanaka, Hikaru; Saito, Hiroshi; Matsuki, Norio

doi:10.1248/cpb.36.4081

Cited by 7 publications

(6 citation statements)

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“…Binding assays were performed according to the methods previously described (Abe et al, 1988;Koike et al, 1988 (Grimm, 1973).…”

Section: Methodsmentioning

confidence: 99%

Role of β‐adrenoceptor‐adenylate cyclase system in the developmental decrease in sensitivity to isoprenaline in foetal and neonatal rat heart

Tanaka¹,

Shigenobu²

1990

British J Pharmacology

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1 The inotropic and chronotropic sensitivity to noradrenaline and isoprenaline (Iso) of foetal and ngonatal rat heart decreases as the heart becomes sympathetically innervated. In the present study, we have examined adenylate cyclase (AC) activation and fl-adrenoceptor binding to determine whether a developmental decrease in sensitivity was demonstrable in the fl-receptor-AC system of atrial and ventricular membranes from the 15 day foetus and 1 day and 7 day neonates. 2 While the maximum activation of AC by Iso increased with age, the sensitivity expressed in terms of pD2 values decreased from the 15th foetal day to the first day after birth in the atria, and from the first day to the 7th day after birth in the ventricle. 3 In contrast, activation of AC by forskolin was almost identical at all ages both in atria and ventricle. 4 The maximum equilibrium binding of [3H]-dihydroalprenolol decreased with age, the dissociation constant being about the same at all ages in both the atria and ventricle. 5 In conclusion, we have demonstrated a developmental decrease in the sensitivity of AC to Iso in myocardial membrane fractions consistent with the developmental decrease in chronotropic and inotropic sensitivity to fl-adrenoceptor agonists. Although a reduction in ,B-adrenoceptor number partly accounts for the decrease in sensitivity, some other factors such as decreased coupling to AC may largely be responsible.

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“…Binding assays were performed according to the methods previously described (Abe et al, 1988;Koike et al, 1988 (Grimm, 1973).…”

Section: Methodsmentioning

confidence: 99%

Role of β‐adrenoceptor‐adenylate cyclase system in the developmental decrease in sensitivity to isoprenaline in foetal and neonatal rat heart

Tanaka¹,

Shigenobu²

1990

British J Pharmacology

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“…We have shown that (3-adrenoceptor mediated responses in suncus ventricle and trachea are very small in comparison with those in rats or guinea pigs and suggest ed deficient coupling between (3-adrenoceptors and adeny late cyclase (9,11). Characteristics of the guanine nucleo tide binding proteins in suncus tissue may be different from those in other species.…”

Section: Discussionmentioning

confidence: 74%

“…We have been characterizing the suncus and found that this animal is a good model for studies on nerve growth factor (2), stress (3), emesis (4), motion sickness (5) and lipid metabolism (6,7). As for the pharmacological properties of their cardiovascular systems, the following unique fea tures were found: norepinephrine decreases the heart rate (8); ~-adrenoceptor-mediated response is deficient in the cardiac muscle (9) and the duration of cardiac action potential is extremely short (10). However, little is known about the pharmacological properties of suncus smooth muscle.…”

Section: Introductionmentioning

confidence: 99%

Adenosine Induces Contractions in Suncus Ileum

Nagata

Saito

Matsuki

1993

Japanese Journal of Pharmacology

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ABSTRACT-Purinoceptor-mediated responses were characterized in the ileum of Suncus murinus. Adenosine as well as adenosine 5 triphosphate (ATP) contracted the ileum in a concentration-dependent manner. Contractile responses to transmural electrical stimulation were attenuated by adenosine only at high concentrations. Theophylline competitively blocked the adenosine-induced contraction. Atropine also inhibited the adenosine-induced contraction but in a non-competitive manner. The ATP-induced contrac tion was not affected by theophylline, atropine or a,13-methylene ATP. Indomethacin shifted the concentra tion-response curves for adenosine and ATP to the right. These results suggest that adenosine elicited con tractions via direct stimulation of postsynaptic PI-purinoceptors and postsynaptic potentiation of the acetylcholine response. Suncus ileum will be a unique model for the analyses of purinoceptor-mediated responses. Keywords:Purinoceptor, Purine nucleotide, Theophylline, Atropine, IndomethacinSuncus murinus (suncus), which belongs to the family Soricidae of the order insectivore, is regarded as the direct ancestor of the primate in the phylogenetic system (1). We have been characterizing the suncus and found that this animal is a good model for studies on nerve growth factor (2), stress (3), emesis (4), motion sickness (5) and lipid metabolism (6, 7). As for the pharmacological properties of their cardiovascular systems, the following unique fea tures were found: norepinephrine decreases the heart rate (8); ~-adrenoceptor-mediated response is deficient in the cardiac muscle (9) and the duration of cardiac action potential is extremely short (10). However, little is known about the pharmacological properties of suncus smooth muscle. In tracheal smooth muscle, the j3-adrenoceptor mediated response is also small (11). Muraki et al. (12) showed that isoproterenol, histamine and neuropeptides cause unique responses of suncus intestine.In the present study, effects of purine derivatives on contraction of suncus ileum were studied for the possible use of the preparation as a new experimental model. The purine derivatives, such as adenosine and adenine nucleo tides, exert several physiological and pharmacological effects on a variety of tissues innervated by the autonomic nervous system (13,14). MATERIALS AND METHODS Recording of mechanical responses of isolated prepara tionsMale adult suncus (50-75 g) were sacrificed, and the in testines were quickly isolated. Since the suncus intestine is short and lacks a cecum, appendix vermiformis and tae nia coli, it is rather difficult to distinguish among the duo denum, jejunum, ileum and colon (15). We regarded the proximal (oral) part of the intestine (of about 3 cm) as the duodenum and the distal (anal) part of 1 cm as the colon. The remainder of the intestine was cut into 3-cm-long pieces and used for experiments as ileal preparations.Each preparation was vertically mounted in a 5 ml-or gan bath containing physiological salt solution of the fol lowing composition: 118.0...

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“…Recent studies from our laboratory have shown that suncus is a unique and useful experimental animal model for research on various subjects such as nerve growth factor (2), stress (3) and emesis (4,5). Moreover, on the pharmacological properties of the cardio vascular systems, we also reported that the 9-adrenergic response in suncus ventricle was markedly smaller in comparison with that in the rat (6). In order to further elucidate (9 adrenoceptor-mediated responses, we studied characteristics of 3-adrenoceptors in tracheal smooth muscle of the suncus in comparison with those of rats and guinea pigs.…”

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confidence: 64%

Deficiency of .BETA.-adrenoceptor-mediated relaxation in Suncus trachea.

et al. 1990

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Abstract-Characteristics of 19-adrenoceptor in the tracheal smooth muscle of Suncus murinus (suncus) were studied in comparison with those of rats and guinea pigs. lsoproterenol induced concentration-dependent relaxation of suncus trachea. However, the maximal relaxation was very small, and about 1000 times higher concentration was necessary compared to the case of the guinea pig. The order of the sensitivity to isoproterenol and the maximal relaxation was guinea pig>>rat> suncus. Tracheae from younger suncus were more sensitive to isoproterenol, but the maximal relaxation was not significantly different from the results using adult animals. Forskolin, a direct activator of adenylate cyclase, relaxed tracheae to similar extents in the three species. Though the affinity of specific [3H]dihydro alprenolol binding was not significantly different, the maximal number of binding sites was in the order of rat>guinea pig>suncus.However, the differences in density of the binding among the three species were not as great as differences in isoproterenol-induced relaxation. These results suggest that 1) Q-adrenoceptor mediated relaxation of tracheal smooth muscle is not well-developed in the suncus and 2) the deficient relaxation is probably caused by insufficient coupling between adrenoceptors and adenylate cyclase.

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Characteristics of cardiac .BETA.-adrenoceptors in Suncus murinus.

Cited by 7 publications

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Role of β‐adrenoceptor‐adenylate cyclase system in the developmental decrease in sensitivity to isoprenaline in foetal and neonatal rat heart

Role of β‐adrenoceptor‐adenylate cyclase system in the developmental decrease in sensitivity to isoprenaline in foetal and neonatal rat heart

Adenosine Induces Contractions in Suncus Ileum

Deficiency of .BETA.-adrenoceptor-mediated relaxation in Suncus trachea.

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