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Am J Physiol Renal Physiol 290: F306-F312, 2006. First published September 27, 2005; doi:10.1152/ajprenal.00062.2005
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Medroxyprogesterone acetate binds the glucocorticoid receptor to stimulate {alpha}-ENaC and sgk1 expression in renal collecting duct epithelia

Christie P. Thomas,1,2,3 Kang Z. Liu,1 and Hemender S. Vats1

1Department of Internal Medicine and the 2Graduate Program in Molecular Biology, University of Iowa College of Medicine, and the 3Veterans Affairs Medical Center, Iowa City, Iowa

Submitted 13 February 2005 ; accepted in final form 23 September 2005

Medroxyprogesterone acetate (MPA), a widely used synthetic progestational contraceptive, occasionally leads to Cushingoid side effects such as hypertension, fluid retention, and centripetal obesity. We investigated the effect of MPA on classic mineralocorticoid target genes, {alpha}-epithelial Na channel (ENaC) and sgk1, in the collecting duct. In adrenalectomized mice, aldosterone, dexamethasone, and MPA increased {alpha}-ENaC mRNA levels in kidney cortex. MPA and dexamethasone, but not progesterone, dose dependently increased {alpha}-ENaC and sgk1 mRNA in M-1 and in Madin-Darby canine kidney-C7 cells, both collecting duct cell lines. The stimulatory effect of MPA and dexamethasone on {alpha}-ENaC expression was inhibited by RU-38486, a combined glucocorticoid receptor (GR) and progesterone receptor (PR) antagonist, but not by Org31710, a pure PR antagonist. MPA and dexamethasone dose dependently increased {alpha}-ENaC promoter-driven luciferase activity in M-1 cells, which was not inhibited by Org31710, indicating that MPA regulates {alpha}-ENaC in a PR-independent manner. When tested in HT29 cells, MPA could only stimulate {alpha}-ENaC-driven reporter activity when GR was coexpressed, confirming the requirement for functional GR in the transcriptional effect of MPA. The activation of steroid receptors such as GR can explain the apparent glucocorticoid effects of MPA, independent of PR activation.

epithelial sodium channel; Na+ transport; aldosterone; glucocorticoid response element


Address for reprint requests and other correspondence: C. P. Thomas, Division of Nephrology, Dept. of Internal Medicine, Univ. of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242-1081 (e-mail: christie-thomas{at}uiowa.edu)




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