Changes in phospholipase a, lipase and cholesterol esterase activity in the aorta in experimental atherosclerosis in the rabbit and rat

Esterase activity has been examined in the aorta of rats given hyperchol-esterolaemic, thrombogenic or atherogenic diets, and rabbits given an atherogenic, semi-synthetic diet low in cholesterol.

In normal rat aorta, the specific activity values are in the numerical order of phospholipase A > lipase > cholesterol esterase. In the rabbit the activities were in the same order but of much lower magnitude.

In the rat, feeding an atherogenic diet containing 40 % peanut oil, 5 % cholesterol and 2 % cholic acid produced an increased phospholipase A and lipase, and a decreased cholesterol esterase activity compared with normal animals. Replacement of peanut oil with butter produced no change in phospholipase A and cholesterol esterase and only a small increase in lipase. Thiouracil depressed the higher lipase and abolished the increased phospholipase A activity of the peanut oil group, and decreased cholesterol esterase in both the butter and peanut oil groups.

In rabbits given the semi-synthetic low cholesterol diet for 10 and 32 weeks, a decrease in phospholipase A and cholesterol esterase activity was seen compared with normal animals. An increased lipase activity was seen at 10 weeks but not at 32 weeks.

It is concluded that the high lipase and low cholesterol esterase activity in the peanut oil fed rat, and the low cholesterol esterase activity in the semi-synthetic diet fed rabbit may be contributing factors in the dietary production of atherosclerosis in these two species.