The Glucose and Lactate Usages of the Diabetic Heart and the Influence of Insulin Thereon

The glucose utilization of the normal dog's heart as studied in a heart‐oxygenator circuit is increased to about 150 mg./100 g./hr., or about double the normal, when the blood glucose is raised to a diabetic level. The lactate usage is thereby slightly reduced to about 150 mg./100 g./hr. 2. The glucose usage of the diabetic dog's heart circulated under comparable conditions with diabetic blood is only about 35 mg./100 g./ hr., and the lactate about 120 mg./100 g./hr. The glucose usage is raised by adding insulin to about 100 mg./100 g./hr., but the lactate thereby reduced to about 90 mg. 3. The fact that the diabetic heart uses lactate at almost the same rate as a hyperglycæmic normal heart is of fundamental importance in the consideration of its metabolism, since it may explain the origin of its glycogen, and also disposes of the need to regard it as dependent solely on the metabolism of protein and fat. If lactate and sugar be regarded for many purposes as mutually interchangeable, then the metabolism of the diabetic heart is only quantitatively different from that of the normal. 4. Certain data concerning fats, unsaponifiable matter, and inositol of the diabetic heart are recorded. The authors express their gratitude to the University of London for a grant from the Thomas Smythe Hughes Medical Research Fund which enabled animals to be purchased. Also to Professor J. C. Drummond and Mr L. Young for help mentioned in the text, and to Messrs Hoffmann La Roche for supply of “Prostigmin” ampoules.