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Increased Activity of Rat Intestinal Lactase Due to Increased Intake of -Saccharides (Starch, Sucrose) in Isocaloric Diets¹

S. Bustamante^*, M. Gasparo, K. Kendall^*, P. Coates, S. Brown, B. Somawane and O. Koldovsky^*,,

^* Department of Pediatrics Department of Physiology, University of Arizona Health Sciences Center, Tucson, AZ 85724 Department of Pediatrics, University of Pennsylvania, Philadelphia, PA 19174

The adapatability of intestinal microvillar -disaccharidases to the variation of -saccharide content in the diet is well established, but the influence of these sugars on the activity of microvillar lactase (neutral ß-galactosidase) has heretofore been considered negligible or non-existing. In two experiments rats were fed isocaloric diets where the carbohydrate (starch or sucrose) content versus fat content was varied. (High carbohydrate diets: 71% of calories as carbohydrate and 5% of calories as fat; low carbohydrate diets: 6 and 73% calories, respectively). Experiment 1: male and female rats had access to experimental diets only from day 12 postnatally and were killed at age 56 days. Experiment 2: male rats were fed experimental diets starting on day 73 postnatally and killed 3, 7, 14 and 28 days later. Rats fed the high carbohydrate diets exhibited a significant increase in activity (specific and total per segment) of lactase in all three intestinal segments compared to rats fed the low carbohydrate diets. Changes in the activity of sucrase and maltase paralleled those of lactase activity. These experiments have thus demonstrated clearly the influence of variation in -saccharide content in the diet upon lactase activity. Further experiments are needed to determine the active principle of this dietary adaptation.

KEY WORDS: • lactase • carbohydrates • sucrase • maltase

¹ Supported by grant AM 27624, NIH, Bethesda, MD.

Manuscript received 9 September 1980.