Gunasegaram R, Peh K L, Loganath A, Chew P C, Shanmugaratnam S
Institute of Science and Forensic Medicine, National Blood Centre, Singapore.
J Perinat Med. 1990;18(6):495-9. doi: 10.1515/jpme.1990.18.6.495.
With a view to establish whether cells of the human umbilical cord possess cholesterol side-chain cleavage activity, homogenates of term umbilical cord obtained following spontaneous vaginal delivery from uncomplicated pregnancies (n = 6; 38-40 weeks gestation) were incubated with 26-14C cholesterol. Controls were homogenates heating in a boiling water bath for 10 min. Proof of the existence of cholesterol C-20, 22-desmolase activity in the viable tissue was established by associating radioactivity due to the labelled carbon 26 of 26-14C cholesterol with the p-bromophenacyl ester of isocaproic acid by reverse-isotope dilution analysis. The desmolase efficiency expressed as specific activity of 14C isocaproic acid, dpm g-1 tissue varied from 110 to 351 with a mean of 202. The small but definite conversion indicates that the cholesterol side-chain cleavage reaction previously believed to be exclusive to the steroidogenic pathway operating in the adrenal, gonads and placenta does exist in the human term umbilical cord in vitro.
为了确定人脐带细胞是否具有胆固醇侧链裂解活性，将从无并发症妊娠（n = 6；妊娠38 - 40周）自然阴道分娩后获得的足月脐带匀浆与26 - 14C胆固醇一起孵育。对照组是在沸水浴中加热10分钟的匀浆。通过反同位素稀释分析，将26 - 14C胆固醇的标记碳26产生的放射性与异己酸对溴苯甲酰酯相关联，从而证实了活组织中存在胆固醇C - 20、22 - 脱氨酶活性。以14C异己酸的比活性表示的脱氨酶效率，dpm g-1组织范围为110至351，平均值为202。这种微小但确定的转化表明，先前认为仅存在于肾上腺、性腺和胎盘中的类固醇生成途径中的胆固醇侧链裂解反应，在体外人足月脐带中确实存在。
