Neuroactive steroids, their precursors, and polar conjugates during parturition and postpartum in maternal and umbilical blood: I. identification andsimultaneous determination of pregnanolone isomers

A rapid method fur the identification and measurement of four pregnanolone isomers and their polar conjugates in human plasma was developed using a si mple quadrupole GC;MS system with electron impact ionization. Steroid level s were measured in the plasma of 13 and three woman at delivery with subara chnoidal and epidural analgesia, respectively, and in corresponding samples of umbilical plasma. A good correlation (r = 0.94. P < 0.001. n = 8) was f ound between the allopregnanolone in maternal plasma determined by GC MS an d that measured by RIA. Epipregnanolone (3<beta>-hydroxy-5 beta -pregenan-2 0-one) was identified and measured for the first time in human plasma; its concentration in both maternal and umbilical plasma was much lower than tha t of other pregnanolone isomers. The levels of 3 beta -hydroxy-pregnanolone isomers were significantly higher in the umbilical plasma than in the mate rnal plasma, while the differences in 3 alpha -hydroxy-isomers were insigni ficant. The differences in conjugates were insignificant except in the case of allopregnanolone, the levels of which were lower in umbilical plasma. I n all of the pregnanolone isomers. a significantly lower conjugated-unconju gated steroid ratio was found in the umbilical plasma than in the maternal plasma. The possible role of the sulfation of pregnanolone isomers around p arturition is discussed. (C) 2001 Elsevier Science Ltd. All rights reserved .