In VivoEffects of Sex Hormones on Aortic Elastin and Collagen Dynamics in Castrated and Intact Male Rats*

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Abstract
The effect of estradiol and testosterone on aortic elastin and collagen dynamics was studied in 5 groups of male rats treated as follows: Group I, castrated, cottonseed oil; Group II, castrated, testosterone; Group III, castrated, estradiol; Group IV, intact, cottonseed oil; Group V, intact, estradiol. After 3 wk of treatment 25 .mu.Ci [14C]proline was injected i.p. into each rat, and rats from each group were killed at 3 h and 3 wk. Specific activity of hydroxyproline in elastin and collagen of aortas was determined. In elastin, testosterone and estradiol caused a decrease in specific activity from 3 h to 3 wk in Groups II-V, compared to castrated oil-treated rats of Group I. In collagen, specific activity declined in Groups II, III and V, compared to Groups I and IV. Specific activity of hydroxyproline in elastin and collagen from the castrated, oil-treated rats did not change between 3 h and 3 wk. The most marked and significant effects were seen in the aortas from Groups III and V, estradiol promoting an increased degradation of the connective tissue proteins. Specific activity of hydroxyproline was higher in elastin than collagen at 3 h and declined more rapidly during the 3 wk period. Estradiol and possibly testosterone increase degradation of aortic elastin and collagen, with estradiol having the most marked effect. In the absence of sex hormones, aortic elastin and collagen are relatively inert. Elastin turnover apparently is greater than that of collagen in aortas of young male rats.