Effect of Dietary Lactose on Intestinal Lactase Activity in Young Rats

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Abstract
To study the effect of dietary lactose on the postweaning decrease in intestinal lactase activity in the rat, mothers with their 1-day-old litters received either a 30% lactose diet or a lactose-free diet containing an equivalent amount of glucose and galactose. The young rats were removed from their mothers at 21 days of age. Lactase, sucrase, and maltase activities were determined in jejunal segments from rats on the two dietary regimens at weekly intervals from 2 to 11 weeks of age. The jejunal lactase activity declined to the low level characteristic of the adult rat between weeks 3 and 4 of life, and there were no significant differences in lactase activity between the controls and lactose-fed rats throughout the entire experiment. Sucrase and maltase activities reached the high levels present in adults when the rats were between 4 and 5 weeks, and 3 weeks of age, respectively. As in the case of lactase activity, no significant differences were found in the jejunal sucrase and maltase levels between the two groups of animals. These findings do not support the hypothesis that intestinal lactase activity can be regulated by administration of dietary lactose.