RAT INTESTINAL SUCRASE: II. THE EFFECTS OF RAT AGE AND SEX AND OF DIET ON SUCRASE ACTIVITY

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Abstract
Intestinal sucrase activity of the rat varies with the age, but not the sex, of the animal. Sucrase activity of rats 23 days of age was approximately two-thirds that of adults.Sucrase activity of adult rats was significantly decreased by several days of fasting. The decrease was rapid during the first 2 to 4 days of the fast, but became negligible thereafter.Diets containing large (70%) amounts of sucrose, galactose, melizitose, or α-methyl-D-glucoside produced highly significant increases in intestinal sucrase levels (compared with a carbohydrate-free, high-casein control diet) when fed ad libitum for 24 hours to adult male rats previously fasted for 3 days. Similar diets containing fructose, fructose plus glucose in equimolar amounts, or maltose significantly increased sucrase activity, but diets containing glucose, mannose, xylose, or lactose were not stimulatory. A 70% raffinose diet significantly decreased sucrase activity. Normal male rats which were fed the 70% sucrose diet for 4 weeks had sucrase activities similar to those of controls fed Purina fox checkers, but animals fed the carbohydrate-free, high-casein diet for 1 day or longer had sucrase activities significantly lower than those of controls. The significance of these observations in regard to enzyme "adaptation" is discussed.