MOVEMENT OF MONOVALENT IONS ACROSS THE MEMBRANES OF MARGINAL CELLS OF THE STRIA VASCULARIS IN THE GUINEA-PIG COCHLEA

The resting potential and monovalent ions in the marginal cells and scala media were measured before and 20 min after the onset of anoxia using ion-sensitive microelectrodes. The resting potential of the marginal cells decreased from 62.7 to -2.4 mV. The K+ activity decreased from 77.7 to 53.2 mEq/l, while the Na+ activity increased from 2.6 to 24.7 mEq/l. The Cl- activity did not change significantly. In the scala media, the endocochlear potential decreased rapidly from 80.9 to -28.0 mV after the onset of anoxia. The K+ activity decreased from 119.0 to 96.5 mEq/l, the Na+ activity increased from 1.3 to 9.5 mEq/l and that of Cl- decreased from 127. 0 to 115.1 mEq/l. The electrochemical gradients determined for each ion based on the ionic changes in the scala media and marginal cells, suggested the existence of an Na/K pump and Na-K-2Cl cotransport at the basolateral membrane of the marginal cells, and a rheogenic K pump and Na-K-2Cl transport at the luminal membrane of the marginal cells. The Na+ and K+ must be recycled at the basolateral membrane and luminal membrane of marginal cells, respectively.