Studies of ultramicrostructure in relation to disaccharidase activity in the jejunal mucosa.

Ultramicrostructural changes of the mucosa of the small intestine were studied in relation to the alterations of the lactase activity, measuring the height of microvilli by electron microscopy and the enzyme activity by the method of Dahlqvist. Studies with clinical cases revealed that the height of microvilli correlated with the lactase activity significantly (p less than 0.01), and that patients with relatively higher microvilli had a correspondingly higher activity of lactase. In animal experiments an increase of lactase activity by lactose load feeding and low calorie feeding resulted in a raise in the height of microvilli. It was concluded that lactase deficiency in adults and in various gastrointestinal diseases, where no histological abnormality was observed by light microscopy is perhaps due to shortening of the microvilli of the mucosa. It was speculated that the microvillous change and the sequential hypolactasia may be the initial ultramicrostructural and enzymatic alteration in the diffuse disease of the small intestine.