Evidence that (+)-bupranolol interacts directly with myocardial β-adrenoceptors

Control of optical purity with differential thermal analysis
  • Wilfried Wächter
  • Ulrich Münch
  • Horst Lemoine
  • Alberto J. Kaumann


Melting points measured with the capillary method were 150.5°C, 150.5°C and 224.0°C for hydrochlorides of (+)-bupranolol, (−)-bupranolol and (±)-bupranolol, respectively. The large difference in melting points of 73.5°C prompted us to determine possible contaminations of (+)-bupranolol with traces of (−)-bupranolol using differential scanning calorimetry. We detected as little as 0.001% (−)-bupranolol in a standard mixture of (+)-bupranolol and (−)-bupranolol. A batch of (+)-bupranolol not measurably contaminated with (−)-bupranolol (optically purity>99.999%) was used in pharmacological and biochemical assays.

The affinities of (−)-bupranolol and (+)-bupranolol were determined functionally by the blockade of isoprenaline stimulation of spontaneously beating rat right atria and electrically driven kitten papillary muscles; and directly by the inhibition of binding of 3H-(−)-propranolol to kitten ventricle membrane particles. In all 3 systems the enantiomeric (−)/(+) affinity ratio was 50–120 for bupranolol. These experiments prove that (+)-bupranolol itself binds to the β-adrenoceptors of mammalian myocardium.

Key words

99.999% (DTA) pure (+)-bupranolol Heart β-adrenoceptors (−)/(+) enantiomeric affinity ratio Inotropism Chronotropism 


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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • Wilfried Wächter
    • 1
  • Ulrich Münch
    • 1
  • Horst Lemoine
    • 2
  • Alberto J. Kaumann
    • 2
  1. 1.Pharmazeutische EntwicklungSanol Schwarz GmbHMonheim
  2. 2.Klinische PhysiologiePhysiologisches Institut der UniversitätDüsseldorfFederal Republic of Germany

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