The effect of isopropylamino radical on the cardiovascular system.

Abstract

1. In order to reexamine ARlENS' hypothesis concerning a relation of an α and β action and the structure of catecholamine, an attempt was made to examine effects of pronethalol and 2-isopropylamino-6 methyl heptane (Metron) on blood pressure and heart rate in dogs. 2. Injection of 5.0 mg/kg of pronethalol caused a slight increase of heart rate and a slight fall of blood pressure, but injection of 10.0 mg/kg resulted in bradycardia and a marked fall of blood pressure. 3. When 2.0 mg/kg of Metron was injected, a transient increase of heart rate and a fall of blood pressure were observed, but after injection of 5.0 mf/kg, a bradycardia and a fall of a blood pressure were caused. When 5.0 mg/kg of Metron was injected after pretreatment of atropine, changes similar to those after injection of 2.0 mg/kg were observed. 4. A slight increase of heart rate and a fall of pressure after injection of pronethalol or Metron seem to indicate a mild β action. But following an increase of dosage of those drugs, a vagal omimetic action appeared, and a β action was not observed. However, pretreatment with atropine reproduced a β action. 5. Pronethalol and Metron had no catechol or phenyl radical, but still possessed a mild β action. Therefore, a β action seemed to relate to isopropylamino radical, and dihydroxyphenyl or hydroxyphenyl radical might be related with an increase of the intensity of a β action.