Expression of retinoic acid receptors and retinoid X receptors in normal and vitamin A deficient adult rat brain.

The importance of retinoic acid and retinoid X receptors (RARs and RXRs) in the metabolism and functioning of the nervous tissue is well documented, but few data are available about the differences on their distribution in males and females, as well as about the possible changes in a vitamin A deficient state (VAD). Therefore, the aim of this study has been to use immunohistochemistry to determine the cellular localization of RARs (α, β, γ) and RXR (α, β, γ) in brain areas in the normal and vitamin A deficient rat, in both males and females. RARα and β isotypes were detected in practically all the male brain areas whereas immunostaining was weak or absent in the female brain except RARα. RXRγ was absent in the female brain, while it was observed in some regions in the male. RXRβ and γ were the most abundant receptors in both sexes, but RXRα were hardly detected in female brain, but were detected more frequently in male. With a vitamin A-free diet, RARs expression was increased in males, but not in females. In the male brain of VAD rats, RXRα expression was increased in some zones and diminished in others. RXRβ and γ expression was decreased in the male brain, but increased or was not modified in those areas of the female brain in which it was observed. These findings indicate that the brain management of retinoic acid differs between males and females, also leading to differences in their response to VAD diet in terms of receptor expression.

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