The identification of novel steroid N-acetylglucosaminides in the urine of pregnant women.

Abstract

A series of pregnanediols and pregnanetriols doubly conjugated with N-acetylglucosamine and glucuronic or sulfuric acid has been identified in urine from pregnant women. Steroid conjugates were separated by ion-exchange chromatography and the glucuronide and monosulfate fractions were analysed by fast atom bombardment mass spectrometry. After removal of the acid moiety, the neutral steroids were isolated, derivatized, and analysed by gas chromatography-mass spectrometry (GC-MS). The analyses revealed the presence of steroids conjugated with N-acetylhexosamine both in the glucuronide and the monosulfate fractions. Following enzyme hydrolysis, the sugar was identified by GC-MS as N-acetylglucosamine (GlcNAc). The major steroid conjugated with GlcNAc both in the glucuronide and monosulfate fractions was identified as 5alpha-pregnane-3alpha,20alpha-diol. 5beta-Pregnane-3alpha,2Oalpha-diol was also present as a GlcNAc conjugate in both fractions whereas a GlcNAc conjugate of 5alpha-pregnane-3beta,20alpha-diol was only found in the sulfate fraction. 5alpha-Pregnane-3alpha,20alpha,21-triol was a double conjugate with GlcNAc in the sulfate fraction whereas a pregnane-2,3,20-triol was a double conjugate in the glucuronide fraction. The positions of conjugation were determined by collision-induced dissociation of the pseudomolecular anions produced by fast atom bombardment ionization. The sulfate and glucuronic acid moieties were located at C-3 and N-acetylglucosamine at C-20. An alternative localization of GlcNAc at C-21 of 5alpha-pregnane-3alpha,20alpha,21-triol cannot be excluded. Judging from the enzymatic hydrolysis of the conjugates, the sugar was attached in beta-glycosidic linkage. The mean excretion of N-acetylglucosaminides of the pregnanediols and pregnanetriols was 32.2 micromol/g creatinine (range 17.9-49.1 micromol) in five healthy women in the 38th-39th week of pregnancy. The mean excretion of 5beta-pregnane-3alpha,20alpha-diol glucuronide in the same women was 71 micromol/g creatinine, (range 27-127 micromol). This indicates that conjugation with N-acetylglucosamine constitutes a quantitatively important pathway of progesterone metabolism in human pregnancy.