Several enzymes involved in the formation of steroids of the pregnene and pregnane series have been identified in the brain, but the biosynthesis of testosterone has never been reported in the central nervous system. In the present study, we have investigated the distribution and bioactivity of 17j8-hydroxysteroid dehydrogenase (1713-HSD) (EC 1.1.1.62; a key enzyme that is required for the formation of testosterone and estradiol) in the brain of the male frog Rana ridibunda. By using an antiserum against human type I placental 17,B-HSD, immunoreactivity was localized in a discrete group of ependymal glial cells bordering the telencephalic ventricles. HPLC analysis of telencephalon and hypothalamus extracts combined with testosterone radioimmunoassay revealed the existence of two peaks coeluting with testosterone and 5a-dihydrotestosterone. After HPLC purification, testosterone was identified by gas chromatography/mass spectrometry. Incubation of telencephalon slices with [3H]pregnenolone resulted in the formation of metabolites which coeluted with progesterone, 17a-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, testosterone, and 5a-dihydrotestosterone. The newly synthesized steroid comigrating with testosterone was selectively immunodetected by using testosterone antibodies. These data indicate that 1718-HSD is expressed in a subpopulation of gliocytes in the frog telencephalon and that telencephalic cells are capable of synthesizing various androgens, including dehydroepiandrosterone, androstenedione, testosterone, and 5a-dihydrotestosterone.

Neurons and glial cells are capable of synthesizing various steroid hormones, but biosynthesis of testosterone in the CNS has never been reported. The aim of the present study was to demonstrate the synthesis of testosterone in the frog brain. The presence of 1 7~3hydroxysteroid dehydrogenase (17~3-HSD)-like immunoreactivity was detected in a population of glial cells located in the telencephalon. Reversed-phase HPLC analysis of brain tissue extracts combined with radioimmunoassay detection revealed the presence of substantial amounts of testosterone and 5a-dihydrotestosterone (5cs-DHT) in the telencephalon where 1 7/3-HSD-positive cells were visualized. In male frogs, castration totally suppressed testosterone and 5a-DHT in the blood and in the rhombencephalon but did not affect the concentration of these two steroids in the telencephalon. Chemical characterization of testosterone in female frog telencephalon extracts was performed by coupling HPLC analysis with gas chromatography-mass spectrometry. Using the pulse-chase technique with [ 3H]pregnenolone as a precursor, the formation of a series of metabolites was observed, including dehydroepiandrosterone, androstenedione, testosterone, 5a-DHT, and estradiol. These data demonstrate the existence of an active form of 1 7f3-HSD in the frog telencephalon, which is likely involved in testosterone biosynthesis within the brain.

A method giving simple access to various 1-(phenylthio)-4-substituted-1,3-dienes (5−10) is described. The influence of the different functionalizations introduced on the dienic systems has been tested in a set of classical [4 + 2] cycloaddition reactions. Both the endo/exo and regio selectivities have been investigated. While the endo compound is, as expected, the only or major isomer in all cases, the regio competition between sulfur and oxygen is in favor of the oxygen substituent in the case studied here, in contrast to related works. For one type of adduct, X-ray crystallographic analysis and NMR spectroscopy have been used in conjunction with ab initio and semiempirical AM1 calculations to determine the structure and conformations of products as well as the energetic pathway from the primary concave endo cycloadduct (28) to a rearranged bicyclic structure (39). The theoretical results fully support the occurrence of a photochemical [1,3] sigmatropic shift of the thiophenyl group.