In vivo evidence for the production of sulfated steroids in the frog brain

II is well established that sulfated neurosteroids are potent regulators of neuronal activity but the biosynthesis of sulfate esters of steroids in th e central nervous system (CNS) has received little attention. In particular , the localization of hydroxysteroid sulfotransferase (HST), the enzyme whi ch is responsible for the formation of sulfated steroids, has never been de termined in the brain. We took advantage of the availability of an antiseru m raised against rat liver I-IST to investigate the distribution of this en zyme in the CNS of the frog Rana ridibunda. Two populations of I-IST-positi ve neurons were localized in the anterior preoptic area and the magnocellul ar nucleus of the hypothalamus. Numerous HST-immunoreactive fibers were vis ualized throughout the telencephalon and the diencephalon. Reversed-phase h igh performance liquid chromatography (HPLC) analysis of frog telencephalon and hypothalamus extracts combined with radioimmunoasssay (RIA) detection showed the presence of substantial amounts of DHEAS-immunoreactive material which coeluted with synthetic DHEAS. The concentrations of DHEAS detected in the telencephalon and hypothalamus were respectively eight and five time s higher than in the serum. The present study demonstrates the occurrence o f HST-immunoreactive material in neurons of the frog telencephalon and dien cephalon. This report also provides evidence for the presence of HST bioact ivity, in vivo, in the frog brain. (C) 2000 Elsevier Science Inc. All right s reserved.