[Experimental dilatation of the cecum and colon in rats. I. Induction by continuous administration of lactose after weaning].

Female weanling Wistar rats, weighing 30-40 g, were allocated into seven groups (I, II, III, IV, V, VI and VII), and given laboratory rat chow containing ascending concentrations of lactose (subgroup L) and sucrose (subgroup S); each group was administered respectively 0, 5, 10, 20, 25, 30 and 35 g of disaccharide per 100 g final weight of diet. The animals were maintained in these diets for 28 days, when they were weighed and sacrificed. The volume of the large intestine was measured, and the weight of cecum and colon were recorded separately. The values were expressed in cm3/100 g of body weight (volume) and g/100 g of body weight (weight of cecum and colon). The results showed that rats given lactose, except group II (L) showed enlargement of the cecum and colon, as revealed by increased volume and weight, proportionally to the concentration of sugar. This increase was more pronounced in the cecum, while the participation of the colon occurred significantly only with high concentrations of lactose (groups VI (L) and VII (L)). Groups V (L), VI (L) and VII (L) showed very low body weights at the end of the experiment and high mortality rates of respectively 37.5, 50 and 80%. It is postulated that the enlargement of the cecum and colon of rats given lactose is probably related to augmented work due to increased fecal flow through the ileo-cecal valve and/or changes in bacterial flora and fermentation. Besides, the low body weight and the high mortality rate of lactose-fed rats may be dependent on the chronic diarrhea observed in these animals.