Expression of 5α-reductase in the human temporal lobe of children and adults

Androgens exert important biological effects on the brain, and 5 alpha-reductase plays a crucial role in androgen metabolism. Therefore, we investigated the expression of the two isozymes of 5 alpha-reductase in the human temporal lobe to determine the predominant isoform and to elucidate the existence of possible sex differences and differences between children and adults. We studied biopsy materials from the temporal lobe of 34 women, 32 men, and 12 children. Quantification of 5 alpha-reductase 1 and 2 messenger ribonucleic acid (mRNA) was achieved by competitive RT-PCR. 5 alpha-Reductase activity was determined in tissue homogenates using [1,2-H-3] androstenedione as the substrate. Only 5 alpha-reductase 1 mRNA was expressed in human temporal lobe tissue; 5 alpha-reductase 2 mRNA was not expressed. 5 alpha-Reductase 1 mRNA concentrations did not differ significantly; in the cerebral cortex of women [25.9 +/-. 7.9 arbitrary units (aU) mean +/- SEM] and men (20.4 +/- 2.8 all) or in the cerebral cortex (23.3 +/- 4.4 all) and the subcortical white matter of adults (32.6 +/- 5.6 all), but they mere significantly higher in the cerebra; cortex of adults than in that of children (6.4 +/- 2.3 aU; P < 0.005). The apparent K-m of 5 alpha-reduction did not show significant differences between the two sexes. In conclusion, 5 alpha-reductase 1 mRNA is expressed in the temporal lobe of children and adults, but 5 alpha-reductase 2 mRNA is not. Sa-Reductase 1 mRNA concentrations did not differ significantly in the sexes, but they were significantly higher in specimens of adults than in those of children.