title: Calcium transport in the endolymphatic sac.
abstract: Ca++ activity and DC potential were measured in vivo in the endolymphatic sac (ES) of guinea pigs by means of double-barrelled ion-sensitive microelectrodes. We found a positive DC potential of 14 mV and a Ca++ activity of 4.7 X 10(-4) M. Anoxia induced a decrease in the DC potential and an increase in Ca++ activity; however, no negative DC potential was measured during permanent anoxia. The Ca++ activity measured was in agreement with the Ca++ value calculated with the Nernst equation, assuming a positive DC potential. On the basis of these data, it was suggested that the Ca++ in the ES is in electrochemical equilibrium with the surrounding fluid and no active Ca++ transport is necessary in the ES of guinea pigs.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D007758:Ear, Inner / Q000378:metabolism*; D004563:Electrochemistry; D004710:Endolymph / Q000378:metabolism; D004712:Endolymphatic Sac / Q000378:metabolism*; D006168:Guinea Pigs; D000860:Hypoxia / Q000378:metabolism; D007474:Ion Exchange; D008839:Microelectrodes
chemical_list: D002118:Calcium