The mechanism of the decrease in serum potassium during insulin-induced hypoglycemia (author's transl)

Abstract

This study was made to investigate the mechanisms of the changes in serum potassium during a period of insulin-induced hypoglycemia. The following experiments were performed: I) A relationship was observed between the amount of insulin dosage and the levels of serum potassium, blood sugar, and plasma cyclic AMP or plasma cyclic GMP in normal controls and rats. In humans, regular insulin (0.025 approximately 0.15 U/kg) was injected intravenously, and blood samples drawn at intervals were used for estimation. Regular insulin (0.1 approximately 1.0 U/kg) was injected into Wistar strain male rats and blood was drawn at intervals. II) A relationship was observed between those items mentioned above in patients with thyroid diseases or diabetes mellitus. They were injected with regular insulin (0.1 U/kg). III) An effect of spironolactone was observed on the levels of the above mentioned items. Regular insulin (0.075 U/kg) was injected into normal controls after the ingestion of spironolactone. IV) An effect of non-selective beta-blocker was observed on the levels of the above mentioned items. Regular insulin (0.1 U/kg) was injected into normal controls and patients with hyperthyroidism after the ingestion of 20 mg of propranolol. The results obtained were as follows: 1) There was a significant logarithmic dose-response relationship between insulin dose and maximum per cent decrease in serum potassium, and maximum per cent increase in plasma cyclic AMP. (p less than 0.02 approximately 0.01) 2) A significant positive correlation was observed between the maximum per cent decrease in serum potassium and the maximum per cent increase in plasma cyclic AMP during the period of insulin-induced hypoglycemia. (p less than 0.001) 3) The changes in serum potassium and plasma cyclic AMP were significantly greater in patients with hyperthyroidism who were possibly in a hyperdynamic beta-adrenergic circulatory state, and these changes were smaller in patients with hypothyroidism than in the normal controls. When their thyroid functions were normalized by the treatment, the changes in serum potassium and plasma cyclic AMP behaved in the same manner as those in the normal controls. 4) Spironolactone had no effect on any change observed in this study. 5) Neither per cent decrease of serum potassium nor per cent increase of cyclic AMP were influenced by propranolol at 15 minutes, but they decreased 30 minutes after the insulin injection. These results may indicate that a decrease of serum potassium levels during the period of insulin-induced hypoglycemia in both the early and late phases is caused by different mechanisms. The change in serum potassium was accompanied by an increase of plasma cyclic AMP, and furthermore this change was inhibited by beta-blocker. It was suggested that beta-adrenoreceptor play a role in a decrease of serum potassium, especially 30 minutes after a injection of insulin.