Abstract
In an attempt to clarify the mechanism of sex-related differences in susceptibility of atherosclerosis, sex-related differences, and fluctuation in lypolytic enzyme activities of rat aorta due to orchiectomy and gonadal hormone treatment were investigated. Sex-related differences in acid cholesteryl ester hydrolase (CEH) activity were slight at 1 month of age but were marked at 2.5 and 6 months. Mature female rats showed significantly higher activity in acid CEH, neutral CEH and lipoprotein lipase (LPL) compared to the age matched male rats. Orchiectomy was performed at weaning and 2 months of age (young and adult castration), and rats were killed at 2.5 or 7 months. Young castration significantly enhanced the acid CEH activity, while adult castration showed only the tendency. LPL activity fluctuated due to castration in a similar way to that of acid CEH. These results of orchiectomy fitted well a hypothesis concerning the sexual differenciation of hepatic metabolism of steroid hormones. Administration of testosterone (100-500μg/kg, s.c. for 2 weeks to months) to female rats markedly decreased acid CEH activity, while administration of 17β-estradiol (100-500μg/kg, s. c. for 2 weeks to 5 months) to male rats only tended to increase the activity. These results indicate 1) that the observed sex-related differences in aortic acid CEH activity may explain at least partly sex-related differences in atherosclerosis, 2) that testosterone rather than estradiol exerted a greater effect on arterial acid CEH activity. A hypothalamicopituitary control of the enzyme activity was discussed.
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