Effect of locally applied drugs on the pH of luminal fluid in the endolymphatic sac of guinea pig

Abstract

The aim of the present work was to assess the effect of various drugs applied locally on the pH of the luminal fluid (pH(lum)) in guinea pig endolymphatic sac. pH(lum) and transepithelial potential, when measured in vivo by means of double-barrelled pH-sensitive microelectrodes, were 7.06 +/- 0.08 and +6.1 +/- 0.34 mV (mean +/- SE; n = 84), respectively, which is consistent with a net acid secretion in the luminal fluid of the endolymphatic sac. Bafilomycin and acetazolamide increased and decreased, respectively, pH(lum). Amiloride, ethylisopropylamiloride, ouabain, and Schering 28080 had no effect on pH(lum). Results obtained with inhibitors of anionic transport systems were inconclusive; e.g., DIDS reduced pH(lum), whereas neither SITS nor triflocin had any effect. We conclude that bafilomycin-sensitive H(+)-ATPase activity accounts for the transepithelial acid gradient measured in the endolymphatic sac and that intracellular and membrane-bound carbonic anhydrase probably participates in regulating endolymphatic sac pH(lum). The relationship between acid pH, endolymph volume, and Ménière's disease remains to be further investigated.

Acid-Sensing Ion Channel 2 Contributes a Major Component to Acid-Evoked Excitatory Responses in Spiral Ganglion Neurons and Plays a Role in Noise Susceptibility of Mice

“…The pH in inner ear fluids is tightly regulated at 7.4 in the cochlea (Wangemann and Schacht, 1996) and 7.0 in the endolymphatic sac (Couloigner et al, 2000). Dysfunction of this acid-base homeostasis in the inner ear fluids is known to affect cochlear functions.…”

Endocytosis of Cationized Ferritin in the Marginal Cells of Stria Vascularis

“…Inlet and outlet holes were made at the basal and apical turns of the cochlea, respectively. CF in an artificial endolymph solution (NaCl 1 mM, KCl 120 mM, CaCl2 0.025 mM, MgCl2 0.025 mM, KH2PO4 1.4 mM, K2HPO4 1.8 mM, KHCO 3 25 mM, Mannitol 25 mM, pH 7.4) [2,4,7,16,26] was perfused into the cochlear duct for five minutes to two hours at a perfusion rate of 2 µl/min using a micropipette. In order to confirm precise insertion of the micropipette into the scala media, the endolymphatic DC potential (EP) was measured by a differential electrometer (Electrometer FD-223; WPI Inc., Sarasota, FL).…”

Endocytosis in the Epithelial Cells of the Endolymphatic Sac

“…The occipital bone was opened, and the ES was exposed by an extradural approach. Three tracers (CF, MPO, and HRP) in an artificial endolymphatic sac endolymph (NaCl 137 mM, KCl 5 mM, CaCl 2 2 mM, MgCl 2 1 mM, NaH 2 PO 4 1 mM, NaHCO 3 12 mM, glucose 11 mM, pH 7.0) [2,4,16,21,27] were infused into the lumen of the ES for 30 min at an infusion rate of 10 ml/min using a micropipette. We set the infusion rate to a high level so as to wash out the homogeneous substances within the lumen of the ES.…”