Effects of optical isomers of clenbuterol on the relaxant response in rat uterus

• Published in: Pharmacological research 2001-02, Vol.43 (2), p.151-154
• Main Authors: Bramuglia, Guillermo F., Rubio, Modesto C.
• Format: Article
• Language: English
• Subjects: Adrenergic beta-Agonists - chemistry; Adrenergic beta-Agonists - pharmacology; Animals; Clenbuterol - chemistry; Clenbuterol - pharmacology; Dose-Response Relationship, Drug; Female; Muscle Relaxation - drug effects; Muscle Relaxation - physiology; Myometrium - drug effects; Myometrium - physiology; Rats; Rats, Wistar; Receptors, Adrenergic, beta-2 - drug effects; Receptors, Adrenergic, beta-2 - physiology; Stereoisomerism; β -adrenoceptors, β -adrenoceptor desensitization, optical isomers
• ISSN: 1043-6618; 1096-1186
• DOI: 10.1006/phrs.2000.0752

Previous works have shown that the administration of the racemic β -adrenoceptor agent clenbuterol produces a desensitization of the relaxant response in rat uterus. The aim of this work was to study the effects of the optical isomers of clenbuterol on the relaxant response in rat uterus. The administration of (l)-clenbuterol (0.25 mg per kg per day) over 1 or 10 consecutive days, produced a reduction of the relaxant response to isoproterenol in uterine rings precontracted with 50 m m KCl from oestrogenic rats. The administration of (d)-clenbuterol (0.25 mg per kg per day) over 1 or 10 days did not affect the relaxant response of isoproterenol. (l)-clenbuterol also produced a concentration-dependent relaxant effect that was not observed with (d)-clenbuterol. These results show that the β -adrenergic relaxant response and the desensitization of the relaxant effect to isoproterenol is due to the (l)-isomer and that the (d)-isomer is not involved in these effects.