Action of Insulin on the Frog (Rana temporaria)

Abstract

EARLIER investigations of the action of insulin on cold-blooded vertebrates have shown that, although large doses usually lead to the appearance of typical convulsions, there is often a long latent period (1–2 days at room temperature) during which there are no visible symptoms^1–3. In experiments performed in March and May 1952 the action of insulin on the blood-sugar level of the frog was followed, at intervals, from the time of injection to the development of convulsions. The frogs were kept at room temperature (17°–20° C.) and were injected with four units of insulin (Wellcome 40) in the dorsal lymph sac. The sugar content of the blood was determined by a modification of the method described by King⁴ for obtaining “true sugar” values, which are 15–20 mgm./100 ml. lower than those previously recorded for the frog⁵.