Dynamics of Epinephrine Distribution in the Dog

¹ From the Department of Physiology, University of Oregon Medical School, Portland, Oregon

The dynamics of epinephrine distribution have been studied in dogs anesthetized with sodium pentobarbital. Epinephrine concentration in blood plasma samples from various sites of the circulatory system during and after constant intravenous infusions of epinephrine was estimated by a fluorometric method. The arterial epinephrine concentration was observed to reach a stable level after several minutes of infusion, the concentration varying directly with the rate of infusion. The disappearance of epinephrine was rapid and of a first order reaction variety. Various sites of epinephrine removal were detected and include the liver, kidney, gut and hindleg but not the lung. A mathematical model is formulated and proposed as a simple functional relation between the rate of infusion, epinephrine concentration, disappearance constant and the volume of distribution. From the data and this model, it was concluded that the epinephrine was not bound irreversibly to plasma constituents and that it was in ‘equilibrium’ with a volume of fluid greater than the intravascular space.