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.
The effects of cortisol, corticotropin and thyroxine on the synthesis of glycerolipids and on the phosphatidate phosphohydrolase activity in rat liver
