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Updated: Sep 10, 2026

Measurement of Smooth Muscle Function in the Isolated Tissue Bath-applications to Pharmacology Research
Published on: January 19, 2015
The sympathomimetic activity of (+/-)-pindolol at beta 1- and beta 2-adrenoceptor sites
Abstract:
In isolated right atrial and stilboestrol-pretreated uterine preparations from both guinea-pigs and rats, pindolol elicited propranolol-sensitive positive chronotropic and smooth muscle relaxant actions. Although the pD2 values for pindolol (8.4-9.2) and (-)-isoprenaline (ISO, 8.4-8.7) fell within the same range in these preparations, the maximum responses to pindolol were less than 15% of those to the catecholamine. Thus, pindolol did not display any selectivity for agonistic actions at beta 1- or beta 2-adrenoceptors. In uteri taken from progesterone-pretreated rats, the pD2 value for (-)-isoprenaline was 9.5 and that of pindolol 8.5. In these preparations the maximal relaxant effect of pindolol (approximately 50% Emax ISO) was greater than that found in oestrogen-pretreated uteri. Thus, it appears that the maximal response of pindolol in vitro can be related to the pD2 value for (-)-isoprenaline. In anesthetized cats, intravenous pindolol elicited non-beta-adrenoceptor-mediated increases in heart rate and decreases in soleus muscle contractility. The mechanism(s) underlying the latter actions are unknown.
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