AJP - Gastrointestinal and Liver Physiology, Vol 247, Issue 6 729-G735, Copyright © 1984 by American Physiological Society
Relation between dietary-induced increase of intestinal lactase activity and lactose digestion and absorption in adult rats
J. Leichter, T. Goda, S. D. Bhandari, S. Bustamante and O. Koldovsky
To study the relation between dietary-induced increase of intestinal
lactase activity and lactose absorption, 11-wk-old rats were fed either a
high-starch (70 cal%), low-fat (7 cal%) diet or a low-starch (5 cal%),
high-fat (73 cal%) diet for 7 days. Food intake and body weight changes
were similar in the two dietary groups. In the first experiment, lactose
absorption was studied in vivo after oral administration of 600 mg lactose
(10% solution in water with added [3H]PEG) to rats fasted for 16 h. Groups
of rats were killed at time 0 and at 1-h intervals for the next 3 h.
Lactase activity and lactose absorption were significantly higher (P less
than 0.01) in the high-starch group than in the low-starch group. In the
subsequent experiment, 9-wk-old rats were fed the two isocaloric diets for
3 days. By use of the everted sac technique, we have demonstrated a
significantly higher absorption of monosaccharides from lactose in the
high-starch diet group; also, glucose transport was higher in the
high-starch diet-fed animals. When Tris, an inhibitor of lactase, was added
into the mucosal fluid, absorption of lactose was abolished and no effect
was seen on glucose absorption (in vivo and in vitro). In both experiments,
significant linear regression was established between lactase activity and
lactose absorption. Our results thus show that the increase in lactase
activity, induced by feeding a high-starch diet to adult rats, is
accompanied by an increased capacity to hydrolyze lactose and absorb the
constituent monosaccharides.
