Control of the hyperpolarization-activated cation current by external anions in rabbit sino-atrial node cells
| Autor: | F Maruoka, A Noma, A M Frace |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Physiology
Sodium Iodide chemistry.chemical_element Cesium Gating Ion Channels Chlorides Animals Reversal potential Cells Cultured Sinoatrial Node chemistry.chemical_classification Membrane potential Dose-Response Relationship Drug Chemistry Conductance Hyperpolarization (biology) Binding constant Electrophysiology Crystallography Biochemistry Potassium Rabbits Ion Channel Gating Research Article |
| Zdroj: | The Journal of physiology. 453 |
| ISSN: | 0022-3751 |
| Popis: | 1. Effects of varying concentrations of anions on the hyperpolarization-activated current (I(f)) were studied in myocytes isolated from the rabbit sino-atrial node. Substituting Cs+ for the intracellular K+ clearly separated I(f) from the delayed rectifier K+ current. Control properties, including gating kinetics and ion selectivity, similar to previous studies were obtained. 2. Substitution of extracellular Cl- with larger anions including isethionate, glutamate, acetate, and aspartate, reduced the amplitude of I(f) without changing the reversal potential. Substitution with small anions such as iodide or nitrate supported an intact I(f). These effects were reproduced in the excised outside-out patch conformation. 3. The conductance for I(f) was a saturating function of the extracellular Cl- concentration ([Cl-]o) with an equilibrium binding constant (K1/2) of 11 mM and a slope factor of about 1 when substituted with large anions. Total removal of small anions completely abolished I(f). 4. The voltage-dependent gating of I(f) was not affected by changing ([Cl-]o), suggesting that Cl- modulates conductance properties of I(f). 5. The results indicate that I(f) conductance is unique in that it is dependent on an extracellular anion (Cl-), yet it is carried exclusively by cations, K+ and Na+. These effects are independent of any measurable voltage-dependent gating parameters. |
| Databáze: | OpenAIRE |
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