title: Cation transport in the ampulla of the semicircular canal and in the endolymphatic sac.
abstract: We examined the effects of anoxia and ethacrynic acid on the endolymphatic potential and cation activity in the superior ampulla of the guinea pig, using double-barrelled ion-exchanger microelectrodes. In normal guinea pigs the ampullar endolymphatic potential was + 3.9 +/- 1.2 mV (n = 32), the Cl- activity 130 +/- 4.6 mM (n = 9), and the Na+ activity 18.4 +/- 4.4 mM (n = 20). After anoxia, the ampullar DC potential decreased rapidly and reversed its polarity within 5 min. It then decreased gradually for 60 min and increased afterwards to approximately zero. K+ activity decreased gradually after a latency of 10 min, whereas Na+ activity increased. During the gradual decrease of a negative ampullar endolymphatic potential, an increase in Na+ activity was observed. Thirty minutes after the intravenous injection of ethacrynic acid (100 mg/kg), the potential began to decrease, changed to a negative polarity, and approached a maximum negative level 100 min after the injection. The decrease in K+ activity corresponded to the reduction of potential whereas Na+ activity remained unchanged. The DC potential of the endolymphatic sac in normal guinea pigs was + 14.7 +/- 5.1 mV (n = 17). The Na+ concentration was 103.3 +/- 14.7 mM (n = 14) and the K+ concentration was 11.6 +/- 0.8 mM (n = 4). After anoxia, the DC potential decreased rapidly and approached 0 mV within 8 min. No negative potential could be observed. The Na+ concentration began to increase 2 min after anoxia and reached the extracellular Na+ concentration about 30 min later.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001692:Biological Transport; D007758:Ear, Inner / Q000098:blood supply / Q000378:metabolism*; D004594:Electrophysiology; D004712:Endolymphatic Sac / Q000378:metabolism*; D004976:Ethacrynic Acid / Q000494:pharmacology; D006168:Guinea Pigs; D007511:Ischemia / Q000378:metabolism; D010100:Oxygen / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D011199:Potentiometry; D012665:Semicircular Canals / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
chemical_list: D012964:Sodium; D004976:Ethacrynic Acid; D011188:Potassium; D010100:Oxygen