Mechanism of Insulin Convulsions. II. Effects of Varying Partial Pressures of Atmospheric O 2,N 2 and CO 2

Abstract

In connection with a study on the relationship between the levels of potassium, inorganic phosphorus and glucose in the blood and the occurrence of insulin convulsions 1 dogs were subjected to atmospheres varying greatly in their partial pressures of O₂, N₂ and CO₂. The finding by Glickman and Gellhorn 2 that rats subjected to lowered O₂ tension (air in low pressure chamber at 460 mm Hg) became more sensitive to insulin and had convulsions sooner than they did in ordinary air, suggested the use of induced anoxic anoxia as an additional means of modifying our experimental conditions. The fact that the convulsions of epilepsy 3 and those of hypoparathyroidism can not infrequently be prevented or aborted by the subject's breathing a gaseous mixture containing 10% CO₂ and 90% O₂ further suggested the desirability of investigating the influence of such alterations in the air breathed on the various constituents of the blood and on the occurrence of convulsions following the administration of insulin.

The method used was that of determining the effects of insulin administration, first, when the experimental animal was allowed to breath room air, and again, one week later when the same animal was kept in an ordinary oxygen tent containing O₂, N₂ and CO₂ at different partial pressures. The insulin was given subcutaneously in large single doses (10 to 25 units per kilo of body weight). In addition to the preliminary control experiments performed on all animals, the following studies were carried out : 17 experiments with low O₂ percentages; 4 with high O₂; 4 with high O₂ plus high CO₂; 4 with low O₂ plus high CO₂, and 10 with high CO₂ plus 20% 0₂. The specific effects of the various gaseous mixtures per se were determined before insulin was administered in some instances.