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Calcium-, voltage- and osmotic stress-sensitive currents in Xenopus oocytes and their relationship to single mechanically gated channels
Article first published online: 12 AUG 2004
DOI: 10.1111/j.1469-7793.2000.t01-2-00083.x
1469-7793/asset/cover.gif?v=1&s=bcbef33af54d55d963e75778fb0863e1dd2cd91b "The Journal of Physiology")
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How to Cite
Zhang, Y. and Hamill, O. P. (2000), Calcium-, voltage- and osmotic stress-sensitive currents in Xenopus oocytes and their relationship to single mechanically gated channels. The Journal of Physiology, 523: 83–99. doi: 10.1111/j.1469-7793.2000.t01-2-00083.x
Publication History
- Issue published online: 13 AUG 2004
- Article first published online: 12 AUG 2004
- (Received 10 June 1999; accepted after revision 10 November 1999)
- Abstract
- Article
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- Cited By
Patch recordings from Xenopus oocytes indicated that mechanically gated (MG) channels are expressed at a uniform surface density (∼1 channel μm−2) with an estimated > 3 × 106 MG channels per oocyte that could generate microamps of current at ±50 mV.
Removal of external Ca2+ induced a membrane conductance that differed from MG channels in ion selectivity, pharmacology and sensitivity to connexion-38.
Depolarization to +50 mV activated a Na+-selective, a Cl−-selective and a non-selective conductance. Hyperpolarization to −150 mV activated a non-selective conductance. None of these conductances appeared to be mediated by MG channels.
Hypotonicity (25 %) failed to evoke any change in membrane conductance in the majority of defolliculated oocytes. Hypertonicity (200 %) evoked a large non-selective (PK/PCl≈ 1) membrane conductance that was not blocked by 100 μM Gd3+.
Although the above stimuli could activate a variety of whole-oocyte conductances, including three novel conductances, they did not involve MG channel activation. Possible mechanisms underlying the discrepancy between observed conductances and those anticipated from patch-clamp studies are discussed.