EFFECT OF ANOXIA ON CONTRACTILITY AND METABOLISM OF INTESTINAL SMOOTH MUSCLE

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Abstract
Segments from the upper portion of rabbit small intestine were subjected to periods of anoxia in vitro. In the presence of glucose, added either at the beginning of the expt. or after the aerobic depletion of the endogenous substrate of the longitudinal smooth muscle, anoxia produced a marked decrease in tone and changed the aerobic contractile pattern characterized by rhythmic longitudinal contractions of regular amplitude, to an anaerobic contraction pattern, characterized by sporadic contractions of variable amplitude. Usually the reintroduction of oxygen produced good recovery of the aerobic contraction pattern, even after 2- and 3-hr. periods of anoxia. If the aerobic depletion of endogenous substrate was followed by no addition of substrate, or by addition of pyruvate, which restores vigorous aerobic contractions, subsequent anoxia, decreased tone, and completely suppressed contractile activity; and the reintroduction of oxygen after 1 hr. usually resulted in no restoration of tone or motility. The ability of glucose to maintain anaerobic contractile activity and to prevent functional damage of the longitudinal muscle over long periods of anoxia has been attributed to its ability to yield energy by means of anaerobic glycolysis. Isolated smooth muscle of dog small intestine exhibited good recovery of high-energy phosphate concn., and rate of oxygen consumption on being returned to aerobic conditions after more than 1 hr. of anoxia.

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