Involvement of Na⁺-H⁺Exchange in Intracellular pH Recovery from Acid Load in the Stria Vascularis of the Guinea-pig Cochlea

Abstract

The effect of acid load by NH4+ prepulse method on intracellular pH (pHi) and Na concentration ([Na+]i) in the stria vascularis tissue was studied using fluorescence ratio image microscopy. The pHi and [Na+]i were determined with fluorescence indicator dyes, 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein and sodium-binding benzofuran isophthalate, respectively. Intracellular acidification from the basal pHi of 7.12 +/- 0.08 to 6.82 +/- 0.08 was induced by NH4+ prepulse. Subsequent addition to the standard NaCl solution gradually increased pHi to the control value. This Na(+)-induced pHi recovery was significantly inhibited by the presence of amiloride and absence of external Na+. Basal free [Na+]i was 19 +/- 5 mM in the stria vascularis. In the same maneuver of acid load, the pHi recovery was associated with the increase in [Na+]i sensitive to the amiloride derivative. Thus, the process of the pHi recovery from acid load was demonstrated to involve the Na(+)-H+ exchange in the stria vascularis.

Gene-Based Deafness Research: Ion Transport and Hearing

“…Med., 2004, 202, 1-11 The hearing organ is a sensory apparatus that converts the mechanical stimulation of sound into electrical energy in the cochlea, and then into a neural code in the central auditory pathway. Electrical phenomena in the cochlea include the endocochlear potential (EP), receptor potential of the sensory hair cells, outer hair cell motility, and neurotransmission, all of which involve the maintenance of the intra-and extracellular chemical and electrical environment (Ikeda et al 1994a). Namely, the fundamental and substantial cellular responses of the cochlear cells are based upon an ion transport system responsible for the electrochemical properties, resulting in the efficient energy-yielding processes of acoustic transduction (Fig.…”

The gastric H,K-ATPase in stria vascularis contributes to pH regulation of cochlear endolymph but not to K secretion

“…H + secretion by marginal cells of the stria vascularis was proposed based on observations of immunostaining of vH + -ATPase near the apical membrane of the epithelial cells [ 3 , 7 ]. H + ,K + -ATPase [ 8 ] and Na + ,H + exchangers [ 9 – 11 ] have been immunolocalized to strial marginal cells and both Na + ,H + exchanger [ 12 ] and H + -monocarboxylate transporter [ 13 ] activity have been observed. A counterbalancing secretion of HCO 3 − by apical pendrin (SLC26A4) in strial spindle cells, spiral prominence and outer sulcus cells is also critical to pH homeostasis and hearing [ 14 ].…”