RT info:eu-repo/semantics/article
T1 Low pO2 selectively inhibits K channel activity in chemoreceptor cells of the mammalian carotid body
A1 López López, José Ramón
A1 González, Constancio
A1 Ureña, J.
A1 López Barneo, José
K1 Neurofisiología
K1 Neurophysiology
AB The hypothesis that changes in environmental 02 tension (pOi) couldaffect the ionic conductances of dissociated type I cells of the carotid body wastested. Cells were subjected to whole-cell patch clamp and ionic currents wererecorded in a control solution with normal pO 2 (pO~ = 150 mmHg) and 3-5 minafter exposure to the same solution with a lower pO,. Na and Ca currents wereunaffected by lowering pO, to 10 mmHg, however, in all cells studied (n = 42)exposure to hypoxia produced a reversible reduction of the K current. In 14 cellsexposed to a pO 2 of 10 mmHg peak K current amplitude decreased to 35 +_ 8% ofthe control value. The effect of low pO2 was independent of the internal Ca 2+concentration and was observed in the absence of internal exogenous nucleotides.Inhibition of K channel activity by hypoxia is a graded phenomenon and in therange between 70 and 120 mmHg, which includes normal pO, values in arterialblood, it is directly correlated with pO 2 levels. Low pO2 appeared to slow down theactivation time course of the K current but deactivation kinetics seemed to beunaltered. Type I cells subjected to current clamp generate large Na- and Cadependentaction potentials repetitively. Exposure to low pO~ produces a 4-10mV increase in the action potential amplitude and a faster depolarization rate ofpacemaker potentials, which leads to an increase in the firing frequency. Repolarizationrate of individual action potentials is, however, unaffected, or slightlyincreased. The selective inhibition of K channel activity by low pO, is a phenomenonwithout precedents in the literature that explains the chemoreceptive propertiesof type I cells. The nature of the interaction of molecular O, with the K channelprotein is unknown, however, it is argued that a hemoglobin-like O, sensor,perhaps coupled to a G protein, could be involved.
PB The Rockefeller University Press
SN 0022-1295
YR 1989
FD 1989
LK http://uvadoc.uva.es/handle/10324/7031
UL http://uvadoc.uva.es/handle/10324/7031
LA eng
NO Journal of General Phisiology, 1989, vol. 93, n. 5. p. 1001-1015
NO Producción Científica
DS UVaDOC
RD 24-nov-2024