THE EFFECT OF TEMPERATURE ON THE INACTIVATION OF EPINEPHRINE IN VIVO AND IN VITRO

¹ Department of Physiology, Stanford University

1. The rate of oxidation of epinephrine by amine oxidase in vitro at graded temperatures can be described by the Arrhenius equation. The value of the thermal increment (µ) for this reaction was 16,618 over the range 5° to 45°C.

2. The effect of injected epinephrine on the contraction of the acutely denervated nictitating membrane of the anesthetized cat was determined at rectal temperatures ranging from 12.9° to 42.3°C.

3. Evidence was presented which indicated that the duration of contraction of the nictitating membrane was a more satisfactory criterion of the rate of inactivation of epinephrine in the hypothermic cat than either the amplitude of contraction or the area under the response curve.

4. For a given dose of epinephrine the response of the nictitating membrane became progressively greater as body temperature was reduced. This was in harmony with the observations on the oxidation of epinephrine by amine oxidase at graded temperatures.

5. Regional warming of the liver (long wave diathermy) of hypothermic cats without change in either rectal temperature or in the temperature of the nictitating membrane shortened the response of the membrane to a given dose of epinephrine.