Dynamics of Na,K-ATPase sites in lateral cochlear wall tissues of the rat

The objective of this study was to determine whether varying levels of either the synthetic glucocorticoid, dexamethasone, or the mineralocorticoid, aldosterone, modulate the quantity of Na,K-ATPase sites in stria vascularis and spiral ligament tissues. Surgically adrenalectomized male rats were administered different dosages of dexamethasone or aldosterone for 7 days and subsequently were sacrificed. Na,K-ATPase alpha-subunits of stria vascularis and spiral ligament homogenates were determined quantitatively by enzyme-linked immunosorbent assay, using a monoclonal antibody shown to react with lateral wall Na,K-ATPase alpha-subunit. Elevated serum levels of dexamethasone were correlated with significantly increased Na,K-ATPase alpha-subunit levels in both the stria vascularis and spiral ligament (P < 0.05). Elevated serum levels of aldosterone were correlated with increased Na,K-ATPase alpha-subunits in the stria vascularis, but not in the spiral ligament (P < 0.1). These data further indicate a positive correlation between increased serum levels of adrenal steroids and induction of Na,K-ATPase synthesis by such steroids, particularly by dexamethasone.