title: Serum profiles of free and conjugated neuroactive pregnanolone isomers in nonpregnant women of fertile age.
abstract: BACKGROUND
  Pregnanolone isomers (PI) with a hydroxy group in the 3alpha-position are neuroinhibitors operating via positive modulation of GABA(A) receptors. The 3beta-PI and sulfates of PI and pregnenolone exert the opposite effect. In addition to the brain's in situ synthesis, some circulating steroids can penetrate the blood-brain barrier.
  
  
  METHODS
  To assess the physiological impact of peripheral endogenous neuroactive pregnanolone isomers and their polar conjugates in women, serum allopregnanolone (P3alpha5alpha), isopregnanolone (P3beta5alpha), pregnanolone (P3alpha5beta), epipregnanolone (P3beta5beta), pregnenolone, estradiol (including their polar conjugates), and additional steroids were measured in 16 women in the follicular and luteal phases of the menstrual cycle using gas chromatography/mass spectrometry and RIA for the analysis. Linear models and Spearman's correlations were used for data evaluation.
  
  
  CONCLUSIONS
  The levels of conjugated PI were from one to almost three orders of magnitude higher in comparison with the free steroids. The results indicate that a substantial proportion of the progesterone is metabolized in the sequence progesterone-->5beta-dihydroprogesterone-->P3alpha5beta-->conjugated P3alpha5beta. The sulfation of PI and particularly of P3alpha5beta moderates the levels of free PI and restrains estradiol biosynthesis via progesterone degradation. PI including the conjugates reflected changing progesterone formation during the menstrual cycle. In the follicular phase, the positive correlation with conjugated pregnenolone, the independence of progesterone, and the negative age relationships of PI indicate their adrenal origin. The dependence on progesterone and the independence of conjugated pregnenolone suggest a gonadal source of PI in the luteal phase. The neuroactivating PI prevailed over neuroinhibiting PI.
authors.affiliation: Institute of Endocrinology, Národní trida 8, CZ 116 94 Prague 1, Czech Republic.
authors.forename: Helena
authors.initials: H
authors.lastname: Havlíková
authors.forename: Martin
authors.initials: M
authors.lastname: Hill
authors.forename: Lyudmila
authors.initials: L
authors.lastname: Kancheva
authors.forename: Jana
authors.initials: J
authors.lastname: Vrbíková
authors.forename: Vladimír
authors.initials: V
authors.lastname: Pouzar
authors.forename: Ivan
authors.initials: I
authors.lastname: Cerny
authors.forename: Radmila
authors.initials: R
authors.lastname: Kancheva
authors.forename: Luboslav
authors.initials: L
authors.lastname: Stárka
mesh_terms: D000328:Adult; D000375:Aging; D003687:Dehydroepiandrosterone / Q000097:blood; D004958:Estradiol / Q000097:blood; D005260:Female; D005498:Follicular Phase; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007536:Isomerism; D008183:Luteal Phase; D011280:Pregnanolone / Q000097:blood* / Q000737:chemistry; D011284:Pregnenolone / Q000097:blood; D011374:Progesterone / Q000097:blood; D011963:Receptors, GABA-A / Q000187:drug effects
chemical_list: D011963:Receptors, GABA-A; C018370:pregnenolone sulfate; D003687:Dehydroepiandrosterone; D011374:Progesterone; D004958:Estradiol; D011284:Pregnenolone; D011280:Pregnanolone