Dimorphic expression of aromatase and 5alpha-reductase in the hypothalamic area during rat development

It is known that Aromatase (Aro), the enzyme which metabolizes androgens into estrogens, and 5alpha-reductase type2 (5α-R2), which specifically forms DHT, increase their expression and activity in late gestation. We have evaluated, by semiquantitative RT-PCR, the existence of a possible dimorphism of these enzymes during development (from gestational day 16 to postnatal day 5) and some of the factors controlling their expression; in particular, the formation of brain speific Aro transcript (containing Exon If) in comparison with the total expression of this enzyme (including variants differing in the 5'-untranslated regions). It has been observed that Aro has two male-specific peaks of expression, before and after birth and only exon If is used in males, while transcripts other than the brain-specific one are also present in females postnatally. Also the 5alpha-R2 expression is higher in males than in females, particularly just after birth. We can conclude that the sexual differentiation of rodent brain probably involves the activation of both Aro and 5alpha-R2 in a sex- and time-specific pattern.