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Potassium channel types in arterial chemoreceptor cells and their selective modulation by oxygen
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ganfornina, Maria D. López-Barneo, José |
| Copyright Year | 1992 |
| Abstract | Single K+ channel currents were recorded in excised membrane patches from dispersed chemoreceptor cells of the rabbit carotid body under conditions that abolish current flow through Na+ and Ca2+ channels. We have found three classes of voltage-gated K+ channels that differ in their single-channel conductance (gamma), dependence on internal Ca2+ (Ca2+i), and sensitivity to changes in O2 tension (PO2). Ca(2+)-activated K+ channels (KCa channels) with gamma approximately 210 pS in symmetrical K+ solutions were observed when [Ca2+]i was greater than 0.1 microM. Small conductance channels with gamma = 16 pS were not affected by [Ca2+]i and they exhibited slow activation and inactivation time courses. In these two channel types open probability (P(open)) was unaffected when exposed to normoxic (PO2 = 140 mmHg) or hypoxic (PO2 approximately 5-10 mmHg) external solutions. A third channel type (referred to as KO2 channel), having an intermediate gamma(approximately 40 pS), was the most frequently recorded. KO2 channels are steeply voltage dependent and not affected by [Ca2+]i, they inactivate almost completely in less than 500 ms, and their P(open) reversibly decreases upon exposure to low PO2. The effect of low PO2 is voltage dependent, being more pronounced at moderately depolarized voltages. At 0 mV, for example, P(open) diminishes to approximately 40% of the control value. The time course of ensemble current averages of KO2 channels is remarkably similar to that of the O2-sensitive K+ current. In addition, ensemble average and macroscopic K+ currents are affected similarly by low PO2. These observations strongly suggest that KO2 channels are the main contributors to the macroscopic K+ current of glomus cells. The reversible inhibition of KO2 channel activity by low PO2 does not desensitize and is not related to the presence of F-, ATP, and GTP-gamma-S at the internal face of the membrane. These results indicate that KO2 channels confer upon glomus cells their unique chemoreceptor properties and that the O2-K+ channel interaction occurs either directly or through an O2 sensor intrinsic to the plasma membrane closely associated with the channel molecule. |
| Starting Page | 401 |
| Ending Page | 426 |
| Page Count | 26 |
| File Format | PDF HTM / HTML |
| PubMed reference number | 1331289 |
| Volume Number | 100 |
| Journal | The Journal of general physiology |
| Alternate Webpage(s) | http://jgp.rupress.org/content/jgp/100/3/401.full.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Adenosine Triphosphate CA2 field Calcium Carotid Body Chemoreceptor Cells Class Fluorides Guanosine Triphosphate Hypoxia Moderate Response Oxygen PO-2 Plasma membrane Sodium Solutions Tension Tissue membrane Voltage-Gated Potassium Channel torr voltage |
| Content Type | Text |
| Resource Type | Article |
