Secretion of colonic isozyme of lysozyme in association with cecotrophy of rabbits.

The relation between the rabbit gastrointestinal (colonic) isozyme of lysozyme and the unique circadial coprophagic behavior of rabbits, termed "cecotrophy," was investigated. We found that lysozyme activity was very low in all segments of the rabbit gastrointestinal tract proximal to the fusus coli. However, the distal or nonsacculated colon, located distal to the fusus coli, had very high lysozyme activity throughout. It was determined, furthermore, that the lysozyme in the wall of the nonsacculated colon was secreted circadially into the colonic lumen in association with the circadial production of soft feces that were destined for reingestion by cecotrophy. The colonic lysozyme, therefore, was transferred to the stomach. These observations suggest that rabbit colonic lysozyme may have a possible function in the upper gastrointestinal tract and be analogous to ruminant abomasal-duodenal lysozyme.