Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog

• Published in: The Journal of physiology Vol. 430; no. 1; pp. 585 - 594
• Main Authors: Valli, P, Zucca, G, Botta, L
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01.11.1990; Blackwell
• Subjects: Action Potentials - drug effects; Animals; Anura; Biological and medical sciences; Calcium - pharmacology; Fundamental and applied biological sciences. Psychology; Hair Cells, Auditory - metabolism; Homeostasis - physiology; In Vitro Techniques; Magnesium - pharmacology; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Ouabain - pharmacology; Perilymph - metabolism; Potassium - metabolism; Rana esculenta; Semicircular Canals - physiology; Tetrodotoxin - pharmacology; Vertebrates: nervous system and sense organs; Frog; Amphibia; Electrophysiology; Homeostasis; Ciliated cell; Salientia; Ionic current; Voltage clamp method; Inner ear; Vertebrata; Semicircular canal; Rana esculenta; Perilymph; Mechanical stimulus; Vestibular system; Potassium
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1990.sp018308

1. Endolymphatic and perilymphatic potassium concentrations were measured with K(+)-sensitive microelectrodes in isolated semicircular canals of the frog. K+ levels were evaluated both at rest and during sinusoidal stimulation (0.05 Hz) of the sensory organ. 2. Mechanical stimulation of hair cells was associated with sinusoidal changes (about 0.2 mM) in the perilymphatic K+ concentration. 3. Perilymphatic K(+)-fluctuations were modified neither by impairment of the synaptic transmission at cyto-neural junctions nor by chronic denervation of the crista ampullaris, thus indicating that K+ ions were actually released by hair cells. 4. Voltage-clamp experiments of the whole sensory organ showed that K+ flows across the crista ampullaris can vary from 3 X 10(11) molecules of K+ s-1 at rest up to about 15 X 10(11) molecules of K+ s-1 during mechanical stimuli. 5. Measurement of intra-ampullar K+ concentration demonstrated that the amount of K+ transported from the perilymph towards the endolymph can be rapidly altered by modifying its perilymphatic levels. This suggests that vestibular organs are endowed with K+ homeostatic mechanisms able to buffer in a very efficient way the concentration of K+ in both the fluids bathing the crista ampullaris. 6. The possible role of K+ homeostatic mechanisms in hair cell adaptation is discussed.