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SummaryA relationship between disaccharidase and diamine oxidase (DAO) activities was looked for by measuring these enzyme activities in histologically normal small intestinal biopsies of 18 children. The range for disaccharidase activities expressed in U g-' wet weight was 0.1-5.7, 7.1-36.7, and 2.3-8.5 for lactase, maltase, and sucrase, respectively. The range for DAO activities expressed in nmol h-' g-' wet weight was 202-974. Significant correlations were found between disaccharidase and DAO activities (lactase versus DAO: n = 17, r = 0.80, P < 0.001; maltase versus DAO: n = 18, r = 0.70, P < 0.001; sucrase versus DAO: n = 18, r = 0.55, P < 0.05). Our results further support the hypothesis that DAO is a marker of small intestinal functional integrity in children.

ABSTRACT. Serum diamine oxidase (DAO) activities were measured in 20 control patients and in 24 patients with gastroenteritis. Results (mean f SE) were as follows: 1) control patients (n = 20), 36.2 2 5.7 pmol h-' ml-I; 2) gastroenteritis (acute phase) (n = l l ) , 31 f 4.9 pmol h-' ml-I; 3) gastroenteritis (healing phase) (n = 21), 18 +. DAO, diamine oxidaseDiamine oxidase is an enzyme showing a high activity in small intestinal mucosal extracts of humans and other mammalian species (6). The enzyme is localized in the cytosol fraction of mature villous enterocytes (2). Mucosal DAO, through its implication in local polyamine and histamine catabolism, is thought to play a role in cell division, as well as a local protective role against histamine (2, 3). We have shown that a positive correlation exists between mucosal DAO and disaccharidase activities in children with a histologically normal duodenal mucosa (5). This supports the hypothesis that mucosal DAO activity reflects mucosal functional integrity. DAO activity is measurable not only in mucosal extracts but also in serum. Further correlation between serum and ileal activities has been shown to exist in the rat (6). The physiological function of circulating DAO is not known.Acute gastroenteritis is accompanied by mucosal destruction and decreased mucosal disaccharidase activities (1). If serum DAO activity accurately reflects small intestinal functional integrity, as stated above, a decrease of serum activities would be

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