Biomaterial Database

pH regulation of the globular substance in the otoconial membrane of the guinea-pig inner ear. 1998

M Tateda, and H Suzuki, and K Ikeda, and T Takasaka

Department of Otorhinolaryngology, Tohoku University School of Medicine, Sendai, Japan.

Physiological and pharmacological characteristics of the globular substance, a precursor of otoconia, are not well understood. In the present study, we investigated the variations and regulation of internal pH (pHi) of the globular substance of the guinea-pig inner ear. The otoconial membrane was dissected out from the utricular macula and loaded with the pH-sensitive fluorophore, carboxyseminaphthorhodafluor-1. Dynamic changes of fluorescence were directly observed under a confocal laser scanning microscope, and pHi was calculated from dual emission ratio. In the NaCl standard solution buffered with 5 mM HEPES/Tris at pH 7.4, the pHi of the globular substance varied from 6.26 to 8.55 with an average of 7.21 (n = 270). Exposure to 25 mM NH+4 induced a rapid increase of the pHi followed by a slow relaxation. The, wash-out of NH+4 caused a prompt and pronounced acidification followed by a gradual pHi recovery to the initial level. This gradual pHi recovery was significantly inhibited by the absence of external Na+, indicating the presence of an external Na(+)-dependent H+ extrusion mechanism. This pHi recovery was also inhibited by 1 mM amiloride and 10 microM 3-amino-N-(aminoiminomethyl)-6-[ethyl(2-propyl)amino]pyrazine-2-ca rboxamide. These results suggest the presence of an Na(+)-H+ exchanger in the globular substance of the guinea pig. However, HCO3(-)-transporting mechanisms were not determined. The working hypothesis for the otoconial formation is discussed.

UI	MeSH Term	Description	Entries
D010037	Otolithic Membrane	A gelatinous membrane overlying the acoustic maculae of SACCULE AND UTRICLE. It contains minute crystalline particles (otoliths) of CALCIUM CARBONATE and protein on its outer surface. In response to head movement, the otoliths shift causing distortion of the vestibular hair cells which transduce nerve signals to the BRAIN for interpretation of equilibrium.	Otoconia,Otoliths,Statoconia,Membrane, Otolithic,Membranes, Otolithic,Otoconias,Otolith,Otolithic Membranes,Statoconias
D002021	Buffers	A chemical system that functions to control the levels of specific ions in solution. When the level of hydrogen ion in solution is controlled the system is called a pH buffer.	Buffer
D002257	Carbonic Anhydrase Inhibitors	A class of compounds that reduces the secretion of H+ ions by the proximal kidney tubule through inhibition of CARBONIC ANHYDRASES.	Carbonate Dehydratase Inhibitor,Carbonate Dehydratase Inhibitors,Carbonic Anhydrase Inhibitor,Carboxyanhydrase Inhibitor,Carboxyanhydrase Inhibitors,Anhydrase Inhibitor, Carbonic,Dehydratase Inhibitor, Carbonate,Inhibitor, Carbonate Dehydratase,Inhibitor, Carbonic Anhydrase,Inhibitor, Carboxyanhydrase,Inhibitors, Carbonate Dehydratase,Inhibitors, Carbonic Anhydrase,Inhibitors, Carboxyanhydrase
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D006859	Hydrogen	The first chemical element in the periodic table with atomic symbol H, and atomic number 1. Protium (atomic weight 1) is by far the most common hydrogen isotope. Hydrogen also exists as the stable isotope DEUTERIUM (atomic weight 2) and the radioactive isotope TRITIUM (atomic weight 3). Hydrogen forms into a diatomic molecule at room temperature and appears as a highly flammable colorless and odorless gas.	Protium,Hydrogen-1
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000086	Acetazolamide	One of the CARBONIC ANHYDRASE INHIBITORS that is sometimes effective against absence seizures. It is sometimes useful also as an adjunct in the treatment of tonic-clonic, myoclonic, and atonic seizures, particularly in women whose seizures occur or are exacerbated at specific times in the menstrual cycle. However, its usefulness is transient often because of rapid development of tolerance. Its antiepileptic effect may be due to its inhibitory effect on brain carbonic anhydrase, which leads to an increased transneuronal chloride gradient, increased chloride current, and increased inhibition. (From Smith and Reynard, Textbook of Pharmacology, 1991, p337)	Acetadiazol,Acetazolam,Acetazolamide Sodium, (Sterile),Acetazolamide, Monosodium Salt,Ak-Zol,Apo-Acetazolamide,Diacarb,Diamox,Diuramide,Défiltran,Edemox,Glauconox,Glaupax,Huma-Zolamide,Ak Zol,AkZol,Apo Acetazolamide,ApoAcetazolamide,Huma Zolamide,HumaZolamide
D000143	Acids	Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. (Grant & Hackh's Chemical Dictionary, 5th ed)	Acid
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001639	Bicarbonates	Inorganic salts that contain the -HCO3 radical. They are an important factor in determining the pH of the blood and the concentration of bicarbonate ions is regulated by the kidney. Levels in the blood are an index of the alkali reserve or buffering capacity.	Bicarbonate,Bicarbonate Ions,Hydrogen Carbonates,Bicarbonate Ion,Carbonic Acid Ions,Hydrogen Carbonate,Carbonate, Hydrogen,Carbonates, Hydrogen,Ion, Bicarbonate,Ions, Bicarbonate,Ions, Carbonic Acid

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