Effects of extracellular ATP on hair cells isolated from the guinea-pig semicircular canals.
Externally applied ATP (100 microM) induced membrane currents in type I and type II vestibular hair cells enzymatically isolated from guinea-pig semicircular canals. In whole-cell voltage-clamp and with 140 mM K+ in the pipette solution, ATP evoked an inwardly directed current in 58% of the cells when held at potentials below -40 mV. In the remainder, external ATP produced an outward current. After block of the K currents, an inward current activated by ATP was revealed at -50 mV. Intracellular Ca2+ levels were monitored using the Ca2+ indicator Fura-2 and were found to rise in both hair cell types in response to ATP. These results strongly suggest that ATP directly controls the entry of Ca2+ into crista hair cells which can then further modulate K+ currents.
Rennie
K J
KJ
Department of Physiology, School of Medical Sciences, University of Bristol, UK.
Ashmore
J F
JF
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002586:Cesium / Q000494:pharmacology; D016257:Fura-2; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology
D015221:Potassium Channels; D002586:Cesium; D000255:Adenosine Triphosphate; D011188:Potassium; D002118:Calcium; D016257:Fura-2