Plasma Electrolytes as Affected by Insulin and by Varying Partial Pressures of Atmospheric Gases

Abstract

In recent studies on the mechanism of insulin convulsions in which the decreases in plasma potassium and inorganic phosphorus, as well as the degree of hypoglycemia, were measured at regular intervals, it was found that the level of blood sugar alone bears a constant relationship to the convulsion. 1 Further experiments on the effects of varying partial pressures of atmospheric gases, O₂, N₂ and CO₂, showed that a drastic lowering of the O₂ content or a marked increase in the CO₂ of the respired air tended to prevent insulin convulsions entirely or greatly to delay their onset in the normal fasting dogs, even when the blood sugar was depressed to levels as low as or lower than those previously observed in the same animals before convulsions. 2 The latter finding indicates that some other factor in addition to hypoglycemia plays a role in the mechanism of insulin convulsions.

In the hope of obtaining further information on this phase of the problem, the present studies pertaining to changes in the plasma electrolyte patterns under the foregoing conditions were undertaken. The procedure followed was that of determining the various electrolytes of the plasma before and at regular intervals after administration of convulsive doses of insulin to fasting unanesthetized dogs, first in room air and subsequently in the various abnormal atmospheres referred to above. No 2 experiments on the same animal were carried out at intervals shorter than one week. The plasma electrolyte patterns were determined as follows: 12 times in 5 normal fasting dogs in room air; 3 times in 3 of the same dogs between 210 and 240 minutes after administering convulsive doses of insulin but before convulsions occurred; twice in 2 of the dogs 15 minutes following the insulin convulsion; 3 times in 3 of these animals after 150 minutes in a tent containing approximately 5% O₂ and 95% CO₂; twice under the latter conditions on 2 of the same dogs but with the administration of previously determined convulsive doses of insulin; twice in 2 dogs after 150 minutes in an atmosphere containing approximately 15% CO₂, 20% O₂ and 65% N₂ and twice in the latter animals under the same conditions but with the administration of large doses of insulin.