Journal of Pharmacological Sciences
Online ISSN : 1347-8648
Print ISSN : 1347-8613
ISSN-L : 1347-8613
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Characterization of Intrinsic Sympathomimetic Activity of Carteolol in Rat Cardiovascular Preparations
Maura FloreaniGuglielmina FroldiMaurizio CavalliSergio BovaMaria Cecilia GironKatia VaraniStefania GessiPier Andrea BoreaMaria Teresa DorigoPaola Dorigo
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2004 Volume 95 Issue 1 Pages 115-123

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Abstract

We evaluated in vitro, in myocardial and vascular preparations isolated from reserpine-treated rats, the intrinsic sympathomimetic activity (ISA) of carteolol, a β12-adrenoceptor blocking agent used in cardiovascular and non-cardiovascular diseases. In spontaneously beating atria, carteolol, at low concentrations (0.01 and 0.1 μM), antagonized the positive inotropic effect of isoprenaline, whereas at higher concentrations (1 μM to 1 mM), it caused an increase in the force of contraction (EC50: 4.6 ± 0.1 μM, Emax: 17.1 ± 1.1%, with respect to the maximum isoprenaline response) and a slight increase (7.8 ± 1.9% over basal values) in the heart rate. The positive inotropic effect of carteolol was abolished by concentrations of propranolol or timolol (10 μM) much higher than those blocking isoprenaline effects in the same preparations. A similar positive inotropic effect was also observed in electrically driven left atrium and in Langendorff perfused hearts. Functional and biochemical evidences supported the involvement of cAMP in the cardiac action of carteolol. In peripheral arteries (femoral and tail) pre-contracted with phenylephrine, carteolol exerted ISA-related relaxing effects, independent of the presence of endothelium and sensitive to high concentrations (10 μM) of conventional β-blockers. On the basis of these results, we propose to categorize carteolol as a non-conventional partial agonist of both cardiac and vascular β-adrenoceptors.

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© The Japanese Pharmacological Society 2004
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