Sex difference in aortic cholesterol esterase activity in rats, and changes of the activity following castration and gonadal hormone treatment

Abstract Sex differences in aortic cholesterol esterase activity and changes in the activity following castration and gonadal hormone treatment were investigated in rats. Differences in the enzyme activity were apparent after 2.5 months and became most significant after 6 months. The activity in the aorta and the liver was significantly higher in female rats. Prepubertal orchiectomy increased the aortic activity, femiinizing the type of metabolism, whereas postpubertal orchiectomy, and both pre- and postpubertal ovariectomy induced no change in the activity. The administration of testosterone to female rats significantly decreased the aortic activity, masculininzing the type of metabolism. However, the administration of testosterone or of 17β-estradiol to male rats had no effect. These results suggest (1) that there are clear sex differences in aortic cholesterol esterase activity, (2) that prepubertal exposure to andogens plays a critical role in the sexual differentiation in aortic and hepatic cholesterol ester metabolism, and (3) that the administration of testosterone can temporarily masculinize the type of metabolism. These results may partly explain the sexual differences in susceptibility to atherosclerosis.