Influence de l'ingestion de yogourtsur l'activité lactasique intestinale chez des souris axéniques ou holoxéniques

Abstract

Summary Two sets of mice just weaned (germ-free or conventional) were fedad 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 thesmall intestine were measured after 14, 28 and 42 days of these diets. The results led to the following conclusions. o 1) Ta and SA were always significantly greater in germ-free andgnotobiotic 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 measurementin 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. The bacterial counts made on the small intestinal walls in the germ-free mice fed with yogurts showed that the measured lactase activity cannot be explained by a supply of bacterial β-galactosidase. These results led us to assess that the ingestion of yogurt stimulates the brush border lactase of the enterocyte. As we can exclude an effect of the lactose present in the yogurt to explain this phenomenon, the stimulation could then be related to the resence of viable yogurt microflora or heat-labile metabolites.