Short-term adaptation of pancreatic hydrolases to nutritional and physiological stimuli in adult rats

Abstract

Abstract o 1. Adult rats, previously maintained on a chow containing 48 p. cent carbohydrates, were fasted 24 h, then refed for 5 days on various diets. The nutritional stimuli were made up either of 4 p. cent corn oil, 67 p. cent of a carbohydrate, and 18 p. cent casein, or of 50 p. cent lipid, 0 p. cent carbohydrates and 18 p. cent casein (w:w). Other rats were simply starved for 3 or 6 days, and a group was diabetic after 7 days on chow, following alloxan administration. 2. The opposite regulations of α-amylase and lipase were striking. The specific activities of both hydrolases tripled within 5 days in the presence of their best inducers (starch and corn oil respectively). The specific activity of the second enzyme decreased simultaneously to one third of its initial value. These variations were reversible. 3. The specific activity of amylase on 67 p. cent starch, glucose, fructose or sucrose did not exceed that on the 48 p. cent carbohydrate chow. The induction by galactose and lactose was mediocre. Amylase decreased sharply during fasting and in diabetic rats. The enzyme was always depressed on fat-diets, but somewhat less so on tricaprylin. 4. When compared to control values on chow, several circumstances favored lipase induction. The specific activity of lipase in the pancreas doubled in diabetic rats. The increase on 67 p. cent galactose was probably due to reduced glucose tolerance. Diets rich in starch, fructose and sucrose also increased lipase. All 50 p. cent fat diets stimulated lipase. Triolein, and various oils (olive, corn, sunflower, walnut and lineseed oils) yielded results twice as good as those with more saturated fats (tricaprylin, tristearin and lard). 5. The activities estimated in the small intestine partially reflected inductions.