pH CHANGES IN RABBIT AND HUMAN STRIATED MUSCLE AFTER CONTRACTION

Abstract

A capillary glass electrode was applied to the study of reaction changes in mammalian striated muscle after contraction in situ in amytalized rabbits and in unanesthe-tized human subjects. In rabbit and human muscle contraction was followed by an identical pattern of pH change. With small amts. of work only alkaline changes resulted followed by gradual return to resting pH level. Greater amts. of work produced a small and short-lived rise of pH followed by a rapid fall of pH. This acid change was then very gradually neutralized. Increased work results in greater acidification at the rate of activity used in these expts. The time required for recovery of resting reaction is related to the degree of acidity developed. Na iodo-acetate heightened the alkaline phase and eliminated the acid phase after contraction in the rabbit. In 3 human subjects greater acidification per unit of work done occurred in previously fatigued than in normal muscles. Work done by human muscle rendered ischemic by a tourniquet was followed by marked acid changes (a fall of 0.71 pH in one case). The reaction changes recorded are probably those occurring in the tissue fluid between the muscle fibers and are not necessarily identical with changes within the fiber itself.