EXPERIMENTS WITH THE PANCREATIC HORMONE INSULIN

(1) Several methods of extraction of the active princple from the total pancreatic tissue are summarized. The authors recommend, to save time and alcohol, the use of sodium chloride or ammonium sulphate during the vacuum distillation of the alcoholic filtrate.(2) The effects of the proteoclastic action of pepsin and trypsin on the hormone were studied with mice as test animals. The results obtained corroborate those of Dudley and of Witzemann and Livshis. By peptic digestion insulin loses about one-fourth of its potency in thirty minutes, one hour being required for the total destruction. The tryptic action is completed in thirty minutes.(3) Insulin reaction in the experimental animals are described. In mice about one-hundredth rabbit unit insulin per ten grams of body weight is required to cause the hypoglycemic reactions with convulsions. This dose caused the typical reactions in 33 and 50% of two lots of fed mice in one hour. In other two lots of fasted animals the percentage of the insulin effect rose to 60 and 65%, where the comatose reaction only has predominated. The authors resort conveniently to the use of mice at least for the preliminary assay of insulin.Young albino rats of 20-50 grams of body weight, with dose of one-hundredth rabbit unit per ten grams of live weight, behave just same as in mice. The older animals over two hundred grams are with the same dose very resistent towards the hypoglycemic convulsions.The insulin convulsions and coma are believed not to occur in pigeon, though the blood sugar level may be easily lowered, with several rabbit units of insulin, to about 50-60% of the normal. The authors describe one rare case of the convulsive reaction in pigeon with two rabbit units dose. The bird convulsed several times during the course of ten hours. The lowest level of the blood sugar was found to be 0, 077 grams per 100c.c.In horse therhypoglycemic convulsions can be easily elicited with one half rabbit units per kilo of body weight. The convulsive blood sugar level was about 0, 050 grams per 100c.c.(4) The efficiency of various sugars in relieving the symptoms caused by insulin in albino rats was studied. The results obtained agree essentially with those of Noble and Macleod in rabbit and of Herring, Irvine and Macleod in mice. Put the quantity of glucose just required (0, 020-0, 025, grams per ten grams of live weight)=1, then mannose=2, maltose=3, fructose>3, galactose>3, and arabinose>4.(5) Insulin exerts no perceptible action on the course of avian beriberi, and vitamin B (oryzanin) has also no influence upon the insulin reactions.