The Effect of Antidiuretic Hormone on Ionic Currents of Strial Marginal Cells in Neonate Rate

Lee, Jun Ho; Kim, Sang Jeong; Kim, Jun; Kim, Ki Whan

Abstract

BACKGROUND AND OBJECTIVES: Strial marginal cells are known to secrete K(+) into endolymph. Slowly activating, voltagede-pendent K(+) channels (I(sK) channels) have been identified in the apical membrane of these cells. Although antidiuretic hormone (vasopressin) has been known to play an important role in the various tissues, its physiological and phamacological roles in the inner ear are still unknown. The purpose of this study is to to investigate the hypothesis that vasopressin increases apical K(+) secretion.
MATERIALS AND METHODS
On-cell macro-patch recordings were made on the apical membrane of strial marginal cells dissected from neonate rat. The effect of vasopressin was compared to the one of raising the bath K(+) concentration.
RESULTS
We observed I(sK) channels in 21 patches (9%) of 235 high resistance seals. When the pipette contained NaCl-pipette solution, raising the bath K(+) concentration from 3.6 mM to 25 mM led to a statistically significant increase in apical outward K(+) current from 0.44+/-0.04 pA to 3.31+/-0.40 pA (n=10). When the bath K(+) concentration was returned to 3.6 mM, the outward current declined to 0.45+/-0.04 pA, which was not statistically different from the original level. Arginine vasopressin (AVP, 10-7 M) increased apical current from 0.43+/-0.04 pA to 2.20+/-0.30 pA (n=10). The current stimulated by elevated AVP was carried by the apical I(sK) channel.
CONCLUSION
Our results demonstrate that AVP receptor is present in marginal cells and that AVP increases transepithelial K(+) secretion by activation of I(sK) channel in neonate rat.