Expression of 5α-Reductase in the Human Temporal Lobe of Children and Adults1

Abstract

Androgens exert important biological effects on the brain, and 5α-reductase plays a crucial role in androgen metabolism. Therefore, we investigated the expression of the two isozymes of 5α-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 5α-reductase 1 and 2 messenger ribonucleic acid (mRNA) was achieved by competitive RT-PCR. 5α-Reductase activity was determined in tissue homogenates using [1,2-3H]androstenedione as the substrate. Only 5α-reductase 1 mRNA was expressed in human temporal lobe tissue; 5α-reductase 2 mRNA was not expressed. 5α-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 aU) or in the cerebral cortex (23.3 ± 4.4 aU) and the subcortical white matter of adults (32.6 ± 5.6 aU), but they were significantly higher in the cerebral cortex of adults than in that of children (6.4 ± 2.3 aU; P < 0.005). The apparent Km of 5α-reduction did not show significant differences between the two sexes. In conclusion, 5α-reductase 1 mRNA is expressed in the temporal lobe of children and adults, but 5α-reductase 2 mRNA is not. 5α-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.