Akao T, Akao T, Aoyama M, Kobashi K
Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
Biochem Pharmacol. 1991 Jun 21;42(1):103-7. doi: 10.1016/0006-2952(91)90687-z.
Glycyrrhetinate (GA) dehydrogenase localized in microsomes of rat liver catalyses the oxidation and reverse reduction of 18 beta-glycyrrhetic acid (GA), an aglycone of glycyrrhizin and a main component of liquorice, to 3-keto-18 beta-glycyrrhetic acid (3-ketoGA). The enzyme activity was detected in microsomes of adult males, but not in those of adult females. It was not observed in infant males but appeared 6 weeks after birth, increased gradually and reached the maximum level at 12 weeks after birth, whereas it was not detected in the hepatic microsomes of females of any age. The administration of estradiol valerate to intact adult males decreased GA dehydrogenase activity remarkably. Castration of male rats also caused a marked reduction of the activity, but the administration of testosterone proprionate to these rats restored it to close to the normal level. On the other hand, ovariectomy of female rats did not bring the activity into existence, but the injection of testosterone proprionate to the ovariectomized rats brought it into a slight existence, in spite of no appearance of the activity by the treatment of testosterone proprionate to intact adult females. The sex-related difference in the activity in adults was eliminated by hypophysectomy of male and female rats, their microsomal activities after the operation being the same, 20-40% of the activity in intact males. Moreover, the administration of estradiol valerate to the hypophysectomized rats did not affect the activity. These results indicate that GA dehydrogenase is male-specific and regulated by sex-hormones through the pituitary.
甘草次酸（GA）脱氢酶定位于大鼠肝脏微粒体中，催化甘草酸苷元、甘草主要成分之一的18β-甘草次酸（GA）氧化并逆向还原为3-酮-18β-甘草次酸（3-酮GA）。该酶活性在成年雄性大鼠的微粒体中可检测到，而成年雌性大鼠的微粒体中未检测到。在雄性幼鼠中未观察到该活性，但在出生后6周出现，逐渐增加并在出生后12周达到最高水平，而在任何年龄段的雌性大鼠肝脏微粒体中均未检测到。给完整的成年雄性大鼠注射戊酸雌二醇可显著降低GA脱氢酶活性。对雄性大鼠进行去势也会导致该活性显著降低，但给这些大鼠注射丙酸睾酮可使其恢复至接近正常水平。另一方面，对雌性大鼠进行卵巢切除并未使该活性出现，但给去卵巢大鼠注射丙酸睾酮可使其稍有活性，尽管对完整成年雌性大鼠注射丙酸睾酮并未使该活性出现。成年大鼠中活性的性别差异通过对雄性和雌性大鼠进行垂体切除而消除，手术后它们的微粒体活性相同，为完整雄性大鼠活性的20 - 40%。此外，给垂体切除的大鼠注射戊酸雌二醇对该活性没有影响。这些结果表明，GA脱氢酶具有雄性特异性，并且通过垂体受性激素调节。
