CARBOHYDRATE AND PHOSPHORUS CHANGES IN PROLONGED MUSCULAR CONTRACTIONS

Abstract

Changes in glycogen, lactic acid, and the P compounds were studied in the muscles of cats subjected to prolonged stimulation in situ at the rates of 1 and 2 twitches per sec. The "steady state" is reached by these muscles within 2 min. At the lower stimulation rate there is no formation of hexosephosphate nor hydrolysis of adenosine triphosphate; at the higher rate both of these changes take place before the steady state is reached, and the latter continues during the steady state. During the steady state any hexosephosphate previously accumulated in the muscle tends to be removed. More than 3 times as much lactic acid is formed in the 1st min. at 2 twitches per sec. as at 1 per sec. Phosphocreatine undergoes hydrolysis when lactic acid is accumulating, and is re-synthesized when lactic acid is lost from the muscle. The steady state is characterized by a continuous formation of lactic acid in small amt.; the rate of this continuous formation depends on the intensity of activity of the muscle. The working muscles absorb large amounts of water from the blood stream.