[Adaptation of rats, after weaning, to a diet with a high concentration of lactose. I. Evaluation of water and diet ingestion].

Twelve female Wistar rats, weaned at 21 days, were allocated in two groups: Lactose Group composed by six rats receiving a normal laboratory diet added with 25 g of lactose for each 100 g of final mixture, and the Saccharose Group that was fed with the same diet but with the lactose being replaced by saccharose in the same proportion; both groups were studied for 28 days. The rats were weighed at the beginning of the experiment and on the 7th, 14th, 21st and 28th days; the relative ingestion of water and diet was evaluated for each animal on the same days except for the first. During the observation period weight gain was significantly lower on the Lactose Group compared to the Saccharose Group, although this difference became less evident towards the end of the experiment. In the Lactose Group the diet ingestion was higher on the 21st and 28th days opposed to the water ingestion which was higher on the 7th and 14th days. The results here presented suggest that, in spite of the ontogenic fall of intestinal lactase in rats, these animals can, even after weaning, accommodate to high doses of dietary lactose, by using adaptative pathways which deserve further investigation.