Expression of 17 beta-hydroxysteroid dehydrogenase types 1, 2, 3 and 4 in the human temporal lobe

Sex steroid hormones exert important biological effects on the brain. Moreo ver, an extensive sex steroid metabolism occurs in the brain. In sex steroi d metabolism 17 beta-hydroxysteroid dehydrogenases (17 beta-HSDs) play esse ntial roles in catalyzing the final steps in androgen and estrogen biosynth esis. Recently four types of human 17 beta-HSDs and a pseudogene of the typ e 1 isoform were identified. To date, 17 beta-HSD has not been extensively studied in the human brain. Therefore, we investigated the mRNA expression of the four isozymes of 17 beta-HSD as well as the pseudogene of the type 1 isoform in the human temporal lobe to determine the predominant isoforms a nd, moreover, to elucidate the existence of possible sex and age difference s. We studied biopsy materials from the temporal lobe of 34 women, 32 men a nd 10 children. Quantification of different mRNAs was achieved by competiti ve reverse transcription-PCR. 17 beta-HSD 1, 17 beta-HSD 3 and 17 beta-HSD 4 were expressed in the human temporal lobe of children and adults, whereas 17 beta-HSD 2 and the pseudogene of 17 beta-HSD I were not expressed. In a dults, 17 beta-HSD 3 and 17 beta-HSD 4 mRNA concentrations were significant ly higher in the subcortical white matter (17 beta-HSD 3: 14 591 +/- 3457 a rbitrary units (aU), mean +/- S.E.M.; 17 beta-HSD 4: 1201 +/- 212 aU) than in the cortex (17 beta-HSD 3: 5428 +/- 1057 aU, P < 0.0002; 17 beta-HSD 4: 675 +/- 74 aU, P < 0.004). 17 beta-HSD 1 concentrations did not differ sign ificantly between the white matter (3860 +/- 1628 aU) and the cortex (2525 +/- 398 aU) of adults. In conclusion, the present study demonstrates the ex pression of 17 beta-HSD 1, 3 and 3 mRNAs in the human temporal lobe. Togeth er with CYP19(AROM) and 5 alpha-reductase, known to be expressed in the hum an brain, the expression of 17 beta-HSD 1, 3 and 4 mRNAs indicates the majo r importance of local steroid biosynthesis in the brain.