title: Asphyxia and diuretic-induced changes in the Ca2+ concentration of endolymph.
abstract: Using Ca2+ -selective microelectrodes based on the neutral carrier, ETH-1001 with polyvinyl chloride (PVC), we have measured changes in the free Ca2+ concentration of guinea pig cochlear endolymph ([Ca](e)) after transient asphyxia or intravenous administration of diuretics. Under the control conditions, the endocochlear potential (EP) was +80 mV, and the [Ca](e) was in the range 1.4 x 10(-7)-2.4 x 10(-6) M (n = 16). Transient asphyxia (1-1.5 min) produced an increase in the [Ca](e) with a fall in the EP, whereas the cessation of the asphyxia led to a quick recovery of both [Ca](e) and EP to their control levels. Intravenous administration of furosemide (60 mg/kg) or bumetanide (30 mg/kg) also caused an increase in the [Ca](e) with a fall in the EP, followed by a gradual recovery of both [Ca](e) and EP. From these results, we obtained a significant correlation between EP and p[Ca](e) (= -log[Ca](e)), and conclude that (1) the [Ca](e) is extremely low, around 10(-6) M or less, under normal conditions and (2) the [Ca](e) is directly correlated with EP under physiological conditions.
authors.affiliation: Department of Physiology II, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, 569-8686 Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Takamaki
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Mori
authors.forename: Michitoshi
authors.initials: M
authors.lastname: Araki
authors.forename: Akihito
authors.initials: A
authors.lastname: Mineharu
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Sohma
authors.forename: Junko
authors.initials: J
authors.lastname: Tashiro
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Yoshida
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takenaka
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kubota
mesh_terms: D000818:Animals; D001237:Asphyxia / Q000378:metabolism*; D002118:Calcium / Q000032:analysis* / Q000378:metabolism*; D003051:Cochlea / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D004232:Diuretics / Q000494:pharmacology*; D004710:Endolymph / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes
chemical_list: D004232:Diuretics; D002118:Calcium