Changes in the content of steroid receptor coactivator-1 and silencing mediator for retinoid and thyroid hormone receptors in the rat brain during the estrous cycle.

In this work, we determined the variations in the content of the steroid receptor coactivator (SRC-1) and the silencing mediator for retinoic acid and thyroid hormone receptors corepressor (SMRT) in the hypothalamus, the preoptic area, and the hippocampus of adult intact rats during the estrous cycle by Western blot. SRC-1 content changed only in the hypothalamus where its lowest content was found on diestrus day with a significant increase at proestrus. This increase was maintained on estrus day. In contrast, SMRT content changed only in the preoptic area where it diminished at metestrus in comparison with the other days of the cycle. SRC-1 content was higher than that of SMRT in the hypothalamus throughout the estrous cycle, whereas SMRT content was higher in the preoptic area. In the hippocampus, there were no significant differences in the content of any cofactor. These results demonstrate that SRC-1 and SMRT content change in a tissue-specific manner in the rat brain during the estrous cycle, and suggest that the transcriptional activity of steroid hormone receptors in the rat brain in physiological conditions is regulated by changes in SRC-1 and SMRT content.