Studies on the Lactic Acid Content of Blood from Normal and Denervated Muscle. ∗

Abstract

These experiments were undertaken to determine whether skeletal muscle deprived of its nerve supply and undergoing the process of atrophy exhibited a lactic acid metabolism similar to that of normal intact muscle. A comparison was made of the lactic acid content of blood entering and leaving a denervated limb with that from the opposite normal limb under the conditions of rest, exercise and adrenalin administration. The studies were made on 5 dogs 2 to 3 weeks after denervation. Simultaneous drawings of blood were made from the femoral artery and femoral veins of dogs under amytal or local procaine anesthesia. The lactic acid was determined in duplicate according to the method of Friedemann, Cotonio and Shaffer. 1 Blood was drawn before and one hour after the subcutaneous injection of 1/5 mg. of adrenalin per kilo of body weight. The exercise was induced by the application of induction shocks at the rate of 2 per second to the muscle groups with needle electrodes. The legs were weighted with a light load to restrict the extent of movement. The exercise was continued for a period of 20 minutes and was in progress at the time the blood was drawn.

A summary of the average results appears in Table I. They indicate that the lactic acid metabolism of skeletal muscle undergoing atrophy of denervation is essentially the same as that of normal muscle as far as can be determined by analysis of blood. The difference between the oxygen content of arterial and venous blood from the exercising limb was more than double the difference noted in the blood from the resting limb. These differences are the only index we have as to the degree of exercise.