Nongenomic effects of corticosteroids on ion transport by stria vascularis.

Stria vascularis electrogenically secretes potassium into endolymph and this secretion is known to be under acute control of several hormone receptors including purinergic, adrenergic and muscarinic receptors. Recently, chronic application of glucocorticosteroid hormones in autoimmune mice was reported to restore both hearing and normal strial morphology. The purpose of this study was to investigate the acute nongenomic effects of glucocorticoids and mineralocorticoid on the short circuit current (I(sc,probe)) across isolated stria vascularis of gerbils using the voltage-sensitive vibrating probe. Application of prednisolone (0.1-30 microM) caused an increase of I(sc,probe) in a dose-dependent manner with an EC50 of 1.1 +/- 0.2 microM (n = 5). Hydrocortisone (10 microM, n = 5) and dexamethasone (10 microM, n = 5) also increased I(sc,probe), but the response was transient and the response rate was faster than for prednisolone. By contrast, aldosterone (10 microM, n = 6) caused a transient decrease of I(sc,probe )within seconds. These results suggest that prednisolone increased secretion of K+ via a nongenomic mechanism in the range of therapeutic plasma concentrations and that this stimulatory effect of glucocorticoids is specific since the mineralocorticoid aldosterone caused a distinctly different response. Copyright 2002 S. Karger AG, Basel