Comparison of sex-steroid synthesis between neonatal and adult rat hippocampus Shimpei Higo a,1 , Yasushi Hojo a,b,c,1 , Hirotaka Ishii a , Toshihiro Kominami a , Kohei Nakajima a , Donald Poirier d , Tetsuya Kimoto a , Suguru Kawato a,b,c, * a Department of Biophysics and Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan b Core Research for Evolutional Science and Technology Project of Japan Science and Technology Agency, The University of Tokyo, Japan c Bioinformatics Project of Japan Science and Technology Agency, The University of Tokyo, Japan d Medicinal Chemistry Division, Oncology and Molecular Endocrinology Research Center, Centre Hospitalier, Universitaire de Quevec Que., Canada G1V 4G2 article info Article history: Received 27 April 2009 Available online 6 May 2009 Keywords: Estradiol Testosterone Hippocampus abstract Sex-steroid synthesis in the hippocampus had been thought to be much more active at the neonatal stage than at the adult stage. However, the detailed comparison between these two stages had not been dem- onstrated yet. Here we performed the comparison about the mRNA level of steroidogenic enzymes and the rate of steroid metabolism between these two stages of the hippocampus. The relative expression level of P450(17a), 17b- or 3b-hydroxysteroid dehydrogenase, or P450arom was approximately 1.3– 1.5-fold higher at the neonatal than at the adult stage. The rate of sex-steroid metabolism (from dehydro- epiandrosterone to estradiol) was 2–7-fold (depending on different steps) more rapid at the neonatal than at the adult stage. Taken together, neonatal steroidogenesis is moderately more active than adult steroidogenesis. Ó 2009 Elsevier Inc. All rights reserved. Introduction Neurosteroidogenesis has been thought to be transiently active at the fetal and neonatal stages and become inactive at the adult stage, because of very low expression of steroidogenic enzymes in the adult [1–3]. The distinct activity of steroidogenesis has been shown in primary cultured astrocytes, oligodendrocytes and neu- rons [4] as well as brain tissues [3,5]. Expression of cytochromes P450(17a), P450arom as well as 17b-hydroxysteroid dehydroge- nase (17b-HSD) and 3b-HSD in the developmental brain has been demonstrated [6]. Relatively high level of sex-steroid content (1– 10 nM) has been observed at the neonatal stages of the brain [7]. In recent years, increasing evidence has accumulated to support the significant adult neurosteroidogenesis or sex-steroidogenesis in the hippocampus [8–11]. These results are achieved by improve- ment of sensitivity of analysis, for example, better primer pair de- sign for RT-PCR analysis. Therefore, the quantitative comparison of neurosteroidogenesis between neonatal and adult stages should be performed. So far, the comparison between neonatal and adult hippocam- pus had not been well demonstrated about mRNA or protein level for steroidogenic enzymes. No direct comparison of sex-steroid production between neonatal and adult stages had been shown. We here compare sex-steroid metabolism in male rat hippo- campus between postnatal 10-day old (P10) and young adult stages. We also compare the expression level of mRNA for steroido- genic enzymes. Materials and methods Animals. Postnatal 10-day male Wistar rats (P10) and young adult rats (12 weeks old) were purchased from Saitama Experi- mental Animals Supply (Japan). All animals were maintained under a 12 h light/12 h dark exposure and free access to food and water. The experimental procedure of this research was approved by the Committee for Animal Research of University of Tokyo. Chemicals. Estradiol (E2), testosterone (T), dihydrotestosterone (DHT), estrone (E1), dehydroepiandrosterone (DHEA), androstene- dione (ADione), pregnenolone (PREG) and progesterone (PROG) were purchased from Sigma (USA). Finasteride was from Aska Pharma Medical. [ 3 H] or [ 14 C] labeled steroids were purchased 0006-291X/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2009.05.005 Abbreviations: ADione, androstenedione; ADiol, androstenediol; DHEA, dehydroepi- androsterone; DHT, dihydrotestosterone; E2, estradiol; E1, estrone; PREG, preg- nenolone; PROG, progesterone; T, testosterone * Corresponding author. Address: Department of Biophysics and Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan. Fax: +81 3 5454 6517. E-mail address: kawato@phys. c.u-tokyo.ac.jp (S. Kawato). 1 Contributed equally to the present work. Biochemical and Biophysical Research Communications 385 (2009) 62–66 Contents lists available at ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc