LOCALIZATION OF VITAMIN-D RECEPTOR IN NORMAL HUMAN DUODENUM AND IN PATIENTS WITH CELIAC-DISEASE

Immunocytochemistry using a specific monoclonal antibody 9A7 gamma was used to identify receptors for calcitriol (1,25 (OH)(2) D-3), the act ive metabolite of vitamin D, in sections of duodenal mucosa. Specific staining for vitamin D receptors was largely restricted to nuclei of e nterocytes lining crypts in duodenal biopsy specimens from normal muco sa. Vitamin D receptors were also abundant in crypts from duodenal muc osa in coeliac disease patients with mucosal damage and villous atroph y. In contrast, alkaline phosphatase, a vitamin D regulated protein, w as absent from crypts but present on brush borders of normal villi, an d on surface enterocytes in coeliac disease. Oestrogen receptor could not be identified in duodenal mucosa. These findings suggest that calc ium malabsorption in coeliac disease does not result from the absence of vitamin D receptors, but rather from reduction in vitamin D regulat ed proteins and functions essential for active calcium absorption that are located in the enterocytes of the villi.