(727.5) Glucocorticoid Hormones Regulate Pendrin Abundance and Subcellular Distribution

Poster Board Number: E198

Delaney Abood (Emory University), Truyen Derek Pham (Emory University), Linda Mullins (University of Edinburgh), John Mullins (University of Edinburgh), Susan Wall (Emory University)

Introduction: Following a low salt diet or aldosterone administration, total and apical plasma membrane pendrin abundance increase through a mechanism thought to involve aldosterone binding to the mineralocorticoid receptor (MR). However, in other cells, aldosterone binding to the MR depends on 11 b Hydroxysteroid Dehydrogenase 2 (11 b HSD2) to oxidize and inactivate glucocorticoids, which are also MR ligands. Although 11 b HSD2 abundance is low or possibly absent in intercalated cells (ICs), it’s abundance might be sufficient to inactivate glucocorticoids, making aldosterone the preferred ligand.  If so, 11 b HSD2 gene ablation should reduce pendrin expression.  Alternatively, the IC MR might preferentially bind another ligand such as glucocorticoids.  To test these possibilities, we examined the effect of 11 b HSD2 gene ablation as well as glucocorticoid administration on pendrin abundance and subcellular distribution.

Methods: 11 b HSD2 KO rats and age-, and sex matched wild type rats on the same background (controls) were given either a diet with a low or high NaCl content for 10 days. Wild type mice were adrenalectomized and given a diet with either zero, normal, or high (i.e. stress level) doses of corticosterone or dexamethasone for 10 days. Pendrin total protein abundance and subcellular distribution were determined in rats and mice from each group by immunoblot and immunohistochemistry.

Results: Both pendrin total protein abundance and pendrin’s relative abundance in the most apical region of the cell were greater in the 11 b HSD2 null than in control rats following either a NaCl-replete or -restricted diet.  Moreover, we observed a dose-dependent increase in both total pendrin abundance and pendrin abundance in the most apical region of the cell following either dexamethasone or corticosterone administration, although the increase appeared greater in mice given corticosterone than dexamethasone.

Conclusions: Glucocorticoids increase pendrin total protein abundance and its relative abundance in the most apical region of the cell.  These results might explain, in part, why pendrin is upregulated in the known absence of 11 b HSD2.