Effect of Adrenalin on Insulin Sensitivity of Partially Adrenalectomized and of Hypophysectomized Dogs

Abstract

In a previous report 1 it was pointed out that after partial adrenalectomy in dogs, the animals became abnormally sensitive to insulin similar to that which is observed after hypophysectomy. This study was undertaken to see if adrenalin injections would delay or prevent the insulin convulsions in partially adrenalectomized and in hypophysectomized dogs. Adrenalin was injected intravenously at a constant rate for a period of 2 hours or less following a single injection of insulin intravenously. The adrenalin was diluted in sterile saline to a concentration such that one cubic centimeter per kilogram of body weight per hour would contain the desired quantity. After adrenalin was discontinued the dogs were observed for several hours for indications of hypoglycemia. Blood sugars were sometimes estimated at intervals during the experiment.

Seven dogs were used in which the dosage of insulin causing convulsions had been carefully determined. A dose of insulin was selected for each animal which consistently produced convulsions in less than 2 hours, usually within one hour. In 3 animals with both adrenals denervated and most of the medullas destroyed, this dose of insulin could be increased 2–4 times without causing convulsions during the injection of adrenalin. In one case, although the animal appeared normal when the injection of adrenalin was stopped at the end of 2 hours, convulsions occurred later. In 2 animals one adrenal had been removed and the other denervated with extensive destruction of the medulla. These animals reacted similarly to the 3 previous ones, one receiving 5 times his usual convulsive dose without showing evidence of hypoglycemia. Two animals which had been hypophysectomized several months before were quite sensitive to insulin. Injections of less than 0.5 unit per kilo regularly produced convulsions. During the administration of adrenalin these animals were able to tolerate much larger doses of insulin, although they were more likely to show convulsions when the adrenalin injection was stopped than the animals with impaired adrenal medulla.