Binding of Adrenaline and Isoprenaline to Plasma Proteins of the Dog

Adrenaline was incubated with dog plasma in concentrations ranging from 50 to 1,000 ng/ml and binding to plasma proteins was found to be about 12% (8, 12 or 14%, as determined by spectrophotofluorimetric, liquid scintillation or Sephadex G-50 gel filtration methods, respectively). For isoprenaline, the binding to plasma proteins was of about 14-18%, as shown by liquid scintillation or Sephadex G-50 gel filtration methods. Cellulose acetate electrophoresis demonstrated that albumin does not play any significant role in this binding, in the case of both adrenaline and isoprenaline. These results show that adrenaline and isoprenaline are much less bound to proteins that noradrenaline (40%). It is concluded that the N substitution present in adrenaline and isoprenaline appears to be responsible for the different degrees of protein binding.