Small intestinal brush border enzymes in cystic fibrosis

The study concerns the maltase, saccharase, lactase and alkaline phosphatas e activity in small intestinal biopsy specimens from 61 consecutively admit ted, untreated, Caucasian cystic fibrosis patients. A group of 319 age matc hed controls admitted during the same time period for undefined gastrointes tinal or nutritional disorders acted as the controls. In order to eliminate morphological damage as a confounding factor, the enz yme activities were studied in small intestinal biopsy specimens having bot h normal stereomicroscopic and histological features. It was shown that nei ther maltase nor saccharase activity was different in the two groups, in co ntrast to lactase and alkaline phophatase activity, that was significantly lower in cystic fibrosis patients. The differences could not be explained b y the nutritional status as judged by the body mass index. Lactase activity is known to be easily affected by numerous enteropathies. As the information on alkaline phosphatase activity is limited, the low act ivity is discussed in more detail. Taking into account the literature data, the low alkaline phophatase activity is tentatively attributed either to e nhanced release from the brush border or to the faulty handling of alkaline phophatase protein in the post-golgi compartments secondary to the accumul ation of incorrectly glycosylated CFTR in the same cell structures.