Previous work has shown that mesenteric infarction causes elevation of total serum creatine phosphokinase (CPK) and each of its three isoenzymes. The exact origin of the CPK has not been determined. Little is known about the actual tissue distribution of CPK in bowel. Experiments were performed to confirm the expectation that CPK was present in the bowel wall and to determine its concentration and the distribution of CPK isoenzymes in the muscularis and mucosa, respectively. Multiple segments were resected from the esophagus, stomach, duodenum, jejunum, ileum, and the proximal and distal colon of normal dogs. The mucosa (MUC) was separated from the seromuscular (MSL) tissue in each of the segments and 1-g samples were analyzed individually for total CPK activity by spectrophotometric analysis and for isoenzyme distribution by agarose gel electrophoresis. The results show that all three isoenzymes of CPK are present throughout the GI tract and that the majority of CPK found is in the MSL. Hence, elevations in serum CPK associated with injuries to the GI tract suggest seromuscular injury. While no isoenzyme is located specifically in the bowel, certain associations were seen. CPK-MM, presumably from striated muscles, was most prevalent in the esophagus. In other portions of the bowel all three isoenzymes were present almost equally. In the mucosa the levels of CPK-MM and CPK-BB always exceeded the level of CPK-MB. Knowledge of the distribution of CPK and its isoenzymes in bowel provides a framework for studying and interpreting serum levels of CPK during bowel injury.
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