Insulin-degrading enzyme (IDE) has been implicated in the intracellular degradation of insulin in insulin target cells. Knowledge of the existence of this enzyme in the intestine will be beneficial to the achievement of clinical oral efficacy of insulin. A comparative study was conducted with rat intestine, human colon adenocarcinoma (Caco-2) cells, and human ileum. Confocal microscopy analysis using the anti-IDE antibody showed that IDE was localized in the mucosal cells of rat and human intestines, as well as in Caco-2 cells. Immunostaining of this enzyme was homogeneous throughout the cell excluding nucleus, indicating a typical cytosolic distribution in rat and human enterocytes and in Caco-2 cells.
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The authors are grateful to Ms. Celest M. Roth for her excellent technical assistance and to Ms. Carol M. Bigalke for her kind assistance. Partial financial support from AAPS Young Investigator Award is acknowledged.