Aromatizing activity of placental microsomal fractions from ewes in late gestation.
Aromatizing activity of placental microsomal fractions from ewes in late gestation.
复制标题
妊娠晚期母羊胎盘微粒体组分的芳香化活性。
作者：
M. R. Mann;L. Curet;A. Colás
用放射性雄烯二酮、睾酮和脱氢表雄酮对8只妊娠136~146日龄家羊胎盘微粒体进行孵育。在皮质醇存在和不存在的情况下检测芳构化活性，并测量雌酮和雌二醇的合成速率。在大多数孵化过程中，雌酮占主导地位，而不是雌二醇，这一结果与人类胎盘的情况相反。在孕育144至146天的胎盘中发现，与睾酮一起孵育的胎盘雌二醇生成率急剧增加，这可能表明芳香化作用的增加比17β-羟基类固醇脱氢酶活性的增加更快。混合物中皮质醇的存在对胎盘芳香化活性没有显著影响，表明皮质醇对体外测定的酶系统没有直接影响。总体平均芳构化活性从4.86正负0.22大幅上升(S.E.M.)胎盘芳香化活性的变化可能是母羊分娩前母羊和胎儿血浆雌激素水平升高的重要原因。
Placental microsomes from eight domestic sheep at 136-146 days of gestation were incubated with radioactive androstenedione, testosterone and dehydroepiandrosterone. Aromatizing activity was examined in the presence and absence of cortisol and the rates of both oestrone and oestradiol synthesis were measured. Oestrone predominated in preference to oestradiol in most of the incubations, a result opposite to that found with human placentae. The sharp increase in the rate of oestradiol production found in the 144- to 146-day-old placentae incubated with testosterone may indicate a more rapid increase of aromatizing than of 17beta-hydroxysteriod dehydrogenase activity. The presence of cortisol in the mixtures did not significantly affect the placental aromatizing activity, indicating that there is no direct effect of cortisol on the enzyme system as measured in vitro. The dramatic rise of overall mean aromatizing activity from 4.86 plus or minus 0.22 (S.E.M.) at 138-141 days of gestation to 12.96 plus or minus 0.38 pmol/mg protein/min at 144-146 days (with a greater relative increase in the rate of oestradiol formation), suggests that changes in placental aromatizing activity may play an important role in maternal and foetal plasma oestrogen surges before ovine parturition.