Duodenal and Renal Transient Receptor Potential Vanilloid 6 Is Regulated by Sex-Steroid Hormones, Estrogen and Progesterone, in Immature Rats

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Transient receptor potential vanilloid 6 (TRPV6) is a major calcium channel located in the apical and basolateral membranes of cells and distributed widely in many other organs, especially the exocrine tissues, intestine, and uterus. Uterine TRPV6 is affected by sex steroid hormonal changes during the estrous cycle and pregnancy. To determine whether sex-steroid hormones influence on the expression of TRPV6 in other tissues, we further examined TRPV6 mRNA expression in the duodenum and kidney by reverse transcriptase- and real-time PCRs, and its protein levels by Western blot analysis and immunohistochemistry (IHC). Immature rats were injected with 17β-estradiol (E2; 40 μg/kg) and/or progesterone (P4; 4 mg/kg) for three days. A treatment with a mixture of E2 and P4 (E2/P4) increased TRPV6 expression in the duodenum, and this increase was maintained when the rats were treated with receptor antagonists of estrogen (ICI 182,780; 10 mg/kg) or progesterone (RU 486; 10 mg/kg) at 30 min before E2/P4 injection. However, no difference was observed in renal TRPV6 protein levels following the treatment with sex-steroid hormones and/or antagonists by Western blot analysis and IHC. These results suggest that duodenal TRPV6 expression may be induced by E2 combined with P4, whereas the renal TRPV6 level is unaffected by these steroids.