Alkaline phosphatase activity in fresh intestinal mucosa and cultured mucosal explants

Alkaline phosphatase (AP) activity is an accepted marker of epithelial cell differentiation and integrity in intestinal mucosal explant systems. In experiments involving AP it is usually expressed as activity per unit protein in tissue culture. It has been previously demonstrated that during organ culture a considerable amount of protein and nucleic acid (NA) may leave the cell and enter the surrounding medium. It may therefore not be appropriate to measure enzyme synthesis in relation to total tissue protein. In this study we attempted to gather additional information on enzyme dynamics and tissue integrity during organ culture of intestinal mucosal explants from children with celiac disease (CD) on a normal diet (ND) (n = 21), children with CD on a gluten-free diet (GFD) (n = 12), and patients with gastrointestinal disorders other than CD (controls) (n = 17). We confirmed the leakage of protein, NA, and AP from the tissue explant into the medium, and normalized the AP data by expressing AP as total AP in tissue plus medium per total NA in tissue plus medium. In patients with CD on a ND, the AP level at time 0 was 9.58 (+/- 12.2) mIU/micrograms NA and after 24 h culture rose to 21.9 (+/- 15.7) mIU/micrograms NA. In patients with CD on a GFD the baseline AP level was 24.9 (+/- 34.8) mIU/micrograms NA, and this value rose after culture to 28.6 (+/- 17.9) mIU/micrograms NA. In the controls the initial AP activity was 17.2 (+/- 15.7) mIU/micrograms NA, and the increase was to 38 (+/- 27.6) mIU/micrograms NA.(ABSTRACT TRUNCATED AT 250 WORDS)