| 10623486 |
Bramuglia GF, Rubio MC: Effects of clenbuterol treatment on the relaxant response in rat uterus. . Pharmacol Res. 2000 Feb;41(2):187-93.
Prolonged treatment with the beta (2)-adrenergic agonist clenbuterol (0.25 mg kg (-1) s.c. once daily for 10 days) produced a reduction of the relaxant response and cAMP production mediated by stimulation of beta-adrenoceptors in oestrogen-treated rat uterus. Substantial decreases in the relaxant effect of isoproterenol is observed in uterine rings precontracted with 50 mM KCl from clenbuterol-treated rats. The recovery of the relaxant response was also studied and significant differences were seen between acute and prolonged treatment with clenbuterol (P <0.05 vs control). In contrast the relaxant effect of forskolin and 3-isobutyl-1-methylxanthine was similar in untreated or treated rats. Sodium fluoride also showed a relaxant response which was not affected by the treatment with clenbuterol. The radioligand studies showed a reduction in the number of beta-adrenoreceptors after acute and prolonged treatment with clenbuterol in rat uterus. These results suggest that prolonged treatment with clenbuterol caused a desensitization of the relaxant uterine response through beta (2)-adrenoceptors and also showed differences in the recovery of the relaxant response depending on the duration of treatment. |
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