1. 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 x 106 MG channels per oocyte that could generate microamps of current at ±50 mV. 2. Removal of external Ca2+ induced a membrane conductance that differed from MG channels in ion selectivity, pharmacology and sensitivity to connexion-38 antisense oligonucleotides. 3. 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. 4. Hypotonicity (25%) failed to evoke any change in membrane conductance in the majority of defolliculated oocytes. Hypertonicity (200%) evoked a large non-selective (P(K/)P(Cl) approximate 1) membrane conductance that was not blocked by 100 μM Gd3+. 5. 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.
|Original language||English (US)|
|Number of pages||17|
|Journal||Journal of Physiology|
|State||Published - Feb 15 2000|
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