The steroid hormones, estrogen and progesterone, are involved mainly in the control of female reproductive functions. Among other effects, estrogen and progesterone can modulate Na⁺ reabsorption along the nephron altering the body’s hydroelectrolyte balance. In this work, we analyzed the expression of cyclic nucleotide-gated channel A1 (CNG-A1) and α1 Na⁺/K⁺-ATPase subunit in the renal cortex and medulla of female ovariectomized rats and female ovariectomized rats subjected to 10 days of 17β-estradiol benzoate (2.0 µg/kg body weight) and progesterone (1.7 mg/kg body weight) replacement. Na⁺/K⁺ ATPase activity was also measured. Immunofluorescence localization of CNG-A1 in the cortex and medulla was performed in control animals. We observed that CNG-A1 is localized at the basolateral membrane of proximal and distal tubules. Female ovariectomized rats showed low expression of CNG-A1 and low expression and activity of Na⁺/K⁺ ATPase in the renal cortex. When female ovariectomized rats were subjected to 17β-estradiol benzoate replacement, normalization of CNG-A1 expression and Na⁺/K⁺ ATPase expression and activity was observed. The replacement of progesterone was not able to recover CNG-A1 expression and Na⁺/K⁺ ATPase expression at the control level. Only the activity of Na⁺/K⁺ ATPase was able to be recovered at control levels in animals subjected to progesterone replacement. No changes in expression and activity were observed in the renal medulla. The expression of CNG-A1 is higher in cortex compared to medulla. In this work, we observed that estrogen and progesterone act in renal tissues modulating CNG-A1 and Na⁺/K⁺ ATPase and these effects could be important in Na⁺ and water balance.

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Tooth eruption requires resorption of the alveolar bone interposed between the tooth germ and the oral mucosa (coronal bone). The cells responsible for bone resorption are the osteoclasts and their activity can be reduced or inactivated by estrogen hormone. We aimed to investigate the effects of estrogen on the process of tooth eruption in rats. Thirty-three Wistar rats, aged two-to-17-days, were divided into control, sham and estrogen-treated groups. After daily injections with estrogen, the animals were euthanized and the jaws removed and processed for histological analysis. We performed clinical examination, morphological analysis, quantification of the number of osteoclasts on the surface of the coronal bone and immunohistochemical analysis of estrogen receptor type alpha (ERα). Estrogen therapy was effective, which could be confirmed by the higher estrogen plasma levels on treated animals. However, it had no effect on tooth development or tooth eruption. Progressive bone resorption was observed and the number of osteoclasts on coronal bone was not affected on hormoneinjected animals, allowing tooth to erupt at the same time observed in untreated animals. Immunohistochemistry for ERα confirmed the presence of this type of receptor in osteoclasts, osteoblasts and osteocytes. Taken together, our results showed that estrogen stimulation was not sufficient to decrease the number of osteoclasts on the coronal bone, supporting the idea that, although estrogen may have a protective activity on bone resorption, this may not apply to the alveolar bone that is meant to be resorbed during eruptive process.