The intact frog (R. pipiens) is both very sensitive to i.v. injection of I-epinephrine (E) in small amounts ( a few micrograms), and very tolerant to large doses (several milligrams) of the hormone. A small dose increased the P.D. and the short circuit current (I,) in skin, and strongly increased the strength of auricular contraction of the heart in vivo; ventricular contractions decreased, and heart rate remained normal. Large doses of E depressed P.D. and I, after, occasionally, elevating both for a brief period following treatment. The mucous glands of the skin emptied their content shortly after E, then began to fill again with secretory materials in spite of uninterrupted E infusions. Ventricular and auricular contractions were remarkably little altered and there were no significant changes in heart rate. Changes were seen, however, in the ECG, e.g.: inversion of the P and T waves. No alteration in the QRS complex or in the rhythm was ever noted. Serum glucose remained within normal limits. A transient calorigenic effect, lasting for 10-20 minutes occurred, in which the O2 consumption rose from a normal of 6 to 7 mI/lOO g/hr to several times this value. Unanesthetized frogs tolerated without great harm 10 mg of E given S.C. within one hour. Signs of prostration and a moderate increase in respiration were noted for some time folIowing treatment. Great tolerance of frogs to hormones which do play a physiological role is also known for thyroxine and insulin, but is especially notable for epinephrine which is least tolerated by warmblooded animals treated with large doses of E. The reasons for these species differences are unknown.Intravenous infusion of several milligrams of epinephrine into anesthetized frogs leads to characteristic changes in electrical potential difference across the skin in. vivo, accompanied by changes in sodium2* flux and in changes in short circuit current (Watlington and Huf, '64; Watlington et al., '64). Alterations in these parameters are also observed, as will be shown below, when very small amounts of epinephrine, ( a few micrograms) are infused through the abdominal vein. Since epinephrine release from the body's own stores is one of several possible mechanisms in the live frog whereby neuroendocrine reflexes could control active ion transport in skin, it became of interest to inquire about the physiological role of epinephrine in the frog, and to focus attention on the great tolerance of frogs to this hormone. To our knowledge the systemic effects of epinephrine in the frog have never been presented in a comprehensive way.Experiments were carried out on the effects of systemically administered epinephrine on the following: Electrical and secretory activity of skin in vivo; dynamics J. CELL. A N D COMP. PHYSIOL., 65: 337-354. of the heart in vivo; electrocardiogram; blood sugar, and total oxygen consumption. The results obtained here and those found widely scattered in the literature are discussed.
METHODSAll experiments were carried out on medium sized and large specime...
