Endogenous ouabain in Ménière’s disease

Objective: Endogenous Ouabain (EO) has been demonstrated to modulate the activity of Na+, K+-ATPase. Our purpose was to measure plasma levels of EO in Meniere's Disease (MD) subjects as a possible predisposing factor to developing and maintaining hydrops. Study Design: Case-control study. Settings: University hospital. Patients: Thirty-nine MD subjects and 29 controls with a lifetime negative history for vertigo and dizziness. Main Outcome Measures: Plasma levels of EO. Results: Plasma EO in MD subjects was in the range between 33 and 504 pmol/L (median, 135.5 pmol/L), whereas in the control group, plasma EO varied between 70 and 724 pmol/L (median, 205 pmol/L). The Mann-Whitney U test detected a statistically significant difference (p = 0.0001). Conclusion: Low plasma levels of EO have been proposed to augment Na-K pump activity, whereas high EO levels show an inhibitory effect on the pump activity. A proper pump activity may be necessary to keep the right ionic amount and osmolarity in endolymph. Although other possibilities may be considered, we suggest that altered control mechanisms of pump activity may be related to the pathogenesis and maintenance of MD.