Mechanism Maintaining the Hyperglycemia of Diabetes.

Abstract

In a previous report 1 it was shown that resting muscle of normal dogs may liberate lactic acid into the blood stream. The lactic acid may thus reach the liver where it is removed and converted to carbohydrate. It may be retained in the liver as glycogen or leave the liver, appearing in the blood as glucose. In the present study on diabetic dogs it was found that this lactic acid-glucose cycle involving muscle and liver was one of the mechanisms for maintaining hyperglycemia after the glycogen stores of the liver were reduced by fasting.

Fourteen large female dogs were fasted for 3 days or more and were then depancreatized under aseptic precautions. When the respiratory quotient and the D/N ratio indicated that the dogs had become completely diabetic, they were put under amytal anesthesia, the femoral vessels were exposed and the abdomen was opened by a longitudinal incision. Samples of blood were drawn practically simultaneously from the femoral artery, femoral vein, portal vein and hepatic vein. These blood samples were analyzed for glucose and lactic acid.

The results may be presented as 3 links in a chain of evidence: First as seen in Table I, both during rest and exercise there is greater concentration of lactic acid in the blood of the femoral vein than in that of the femoral artery. Taking differences of 5 mg. % or more as significant, this occurred in 13 of 25 observations. Only once did the muscles take out lactic acid from the blood.