[Effect of yogurt ingestion on the intestinal lactase activity in axenic or holoxenic mice].

Two sets of mice just weaned (germ-free or conventional) were fed ad libitum with three different diets: a 5% lactose solution, yogurt at a 3/5 dilution in this lactose solution, and heated yogurt at the same dilution in the same solution. Total lactase activity (TA) and specific lactase activity (SA) of the small intestine were measured after 14, 28 and 42 days of these diets. The results led to the following conclusions. 1) TA and SA were always significantly greater in germ-free and gnotobiotic animals than in conventional ones, whatever the diets and age of the animals. 2) TA and SA were significantly greater at the three times of measurement in the gnotobiotic and conventional animals fed with unheated yogurt than in the animals fed with heated yogurt. The 5% lactose solution gave intermediate results. 3) In conventional and gnotobiotic animals fed with yogurt, TA increased with time compared to the initial value at weaning. With the two other diets, TA remained constant or decreased. With yogurt, SA varied only weakly with time compared to weaning values, when it decreased in greater proportions with the two other diets.