HOMEPRODUCTSCOMPANYCONTACTFAQResearchDictionaryPharmaSign Up FREE or Login

Endolymphatic perfusion with EGTA-acetoxymethyl ester inhibits asphyxia- and furosemide-induced decrease in endocochlear potential in guinea pigs.

Abstract
We examined the effect of the Ca(2+) concentration in the endolymph ([Ca](e)) or in the endolymphatic surface cells ([Ca](i)) on the endocochlear potential (EP) by using an endolymphatic or perilymphatic perfusion technique, respectively. (i) A large increase in [Ca](e) up to approximately 10(-3) M with a fall in the EP was induced by transient asphyxia ( approximately 2 min) or by the intravenous administration of furosemide (60 mg/kg), and a significant correlation was obtained between the EP and p[Ca](e) (= -log [Ca](e), r = 0.998). (ii) Perfusion of the endolymph with 10 mM EGTA for 5 min neither produced any significant change in the EP nor altered the asphyxia-induced change in EP (DeltaEP(asp)), suggesting that neither [Ca](e) nor the Ca(2+) concentration gradient across the stria vascularis contributed directly to the generation of the EP in the condition of low [Ca](e). In contrast, endolymphatic perfusion with high Ca(2+) (more than 10 mM) produced a decrease in EP and a significant correlation was obtained between the EP and the Ca(2+) concentration of perfusion solution (r = 0.982), suggesting that Ca(2+) permeability may exist across the stria vascularis. (iii) The administration of a Ca(2+) chelator, EGTA-acetoxymethyl ester (AM, 0.3 mM), to the endolymph, which produced a gradual increase in EP, suppressed significantly, by 60-80%, DeltaEP(asp) or furosemide-induced changes in EP. In contrast, perilymphatic administration of 0.5 mM EGTA-AM caused no significant suppression of the DeltaEP(asp). These findings suggest that [Ca](i) plays an important role in generating/maintaining a large positive EP.
AuthorsAkihito Mineharu, Yoshiaki Mori, Yoshitsugu Nimura, Atsuko Takamaki, Michitoshi Araki, Junko Yamaji, Ryotaro Yoshida, Hiroshi Takenaka, Takahiro Kubota
JournalThe Japanese journal of physiology (Jpn J Physiol) Vol. 55 Issue 1 Pg. 53-60 (Feb 2005) ISSN: 0021-521X [Print] Japan
PMID15796789 (Publication Type: Journal Article)
Chemical References
  • Chelating Agents
  • Diuretics
  • Egtazic Acid
  • Furosemide
  • EGTA acetoxymethyl ester
  • Calcium
Topics
  • Animals
  • Asphyxia (metabolism, physiopathology)
  • Calcium (metabolism)
  • Chelating Agents (pharmacology)
  • Cochlea (physiology)
  • Cochlear Microphonic Potentials (drug effects, physiology)
  • Diuretics (pharmacology)
  • Egtazic Acid (analogs & derivatives, pharmacology)
  • Endolymph (drug effects, physiology)
  • Furosemide (pharmacology)
  • Guinea Pigs
  • Microelectrodes
  • Perfusion
  • Perilymph (drug effects, physiology)

Join CureHunter, for free Research Interface BASIC access!

Take advantage of free CureHunter research engine access to explore the best drug and treatment options for any disease. Find out why thousands of doctors, pharma researchers and patient activists around the world use CureHunter every day.
Realize the full power of the drug-disease research graph!


Choose Username:
Email:
Password:
Verify Password:
Enter Code Shown: