Fukuda T, Hirato K, Yanaihara T, Nakayama T
Endocrinol Jpn. 1986 Jun;33(3):361-8. doi: 10.1507/endocrj1954.33.361.
Placental 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) activity was studied in order to evaluate the mechanism of continuation of pregnancy and initiation of labor. The placentas obtained at various gestational weeks were homogenized and fractionated into "nuclear", "mitochondrial", "microsomal" and "supernatant" fractions. Each fraction was incubated with 14C-progesterone and a hydrogen donor. Enzymatic activity was measured by the conversion of progesterone to 20 alpha-dihydroprogesterone. The highest activity of 20 alpha-HSD for progesterone was found to be localized in "microsomal" fraction. The Km constant of 20 alpha-HSD was 4.5 X 10(-6)M for progesterone in "microsomal" fraction. It was found that placental microsomal 20 alpha-HSD required NADPH as well as NADH. 20 alpha-HSD activity for progesterone increased as gestational weeks advanced. The addition of DHA-sulfate and DHA inhibited 20 alpha-HSD activity for progesterone significantly, suggesting that the steroid produced by the feto-placental unit may be involved in the metabolism of progesterone in human placenta.
为了评估妊娠持续和分娩发动的机制，对胎盘20α-羟类固醇脱氢酶（20α-HSD）活性进行了研究。将在不同孕周获得的胎盘匀浆，并分离成“细胞核”、“线粒体”、“微粒体”和“上清液”部分。将每个部分与14C-孕酮和氢供体一起孵育。通过孕酮转化为20α-二氢孕酮来测定酶活性。发现20α-HSD对孕酮的最高活性定位于“微粒体”部分。在“微粒体”部分中，20α-HSD对孕酮的Km常数为4.5×10^(-6)M。发现胎盘微粒体20α-HSD需要NADPH以及NADH。随着孕周的增加，20α-HSD对孕酮的活性增加。添加硫酸DHA和DHA可显著抑制20α-HSD对孕酮的活性，这表明胎儿-胎盘单位产生的类固醇可能参与人胎盘中孕酮的代谢。
