Lactic acid in mammalian cardiac muscle.—Part II. The rigor mortis maximum and the normal glycogen content

Abstract

In Part I of this paper two of us have shown that the stimulation maximum is different in mammalian cardiac and skeletal muscle. The heart muscle has only about one-third of the lactic acid concentration of the skeletal muscle, when both no longer respond to stimulation. We suggested as one possible explanation the fact that the heart normally might not contain as much lactic acid precursor as the skeletal muscle. In the present investigation the total amount of lactic acid produced in ordinary rigor mortis, and in the rigor mortis induced by the use of buffered phosphate solutions of caffeine, was determined. Cats were used as in the preceding experiments. In the first series of observations the ordinary rigor mortis formation of lactic acid was determined. The usual procedure was to take a limb (or a pair of limbs) from a cat used in the stimulation maximum experiment, and to place it for three hours in an incubator kept at 37° C. Along with the muscle were put either both ventricles or the portion that remained after a sample had been taken for determination of the stimulation maximum. After incubation the tissues were treated as described in Part I, and their lactic acid content measured.