Functional sensitivity of the native skeletal Ca2+-release channel to divalent cations and the Mg–ATP complex
| Autor: | Diane Savaria, Janet Pinkos, Eric Rousseau |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Sucrose
Ruthenium red Cations Divalent Physiology Voltage clamp Analytical chemistry chemistry.chemical_element In Vitro Techniques Calcium Divalent chemistry.chemical_compound Adenosine Triphosphate Adenine nucleotide Microsomes Physiology (medical) medicine Animals Pharmacology chemistry.chemical_classification Voltage-dependent calcium channel Calcium Radioisotopes Muscles Proteins Skeletal muscle General Medicine Microscopy Electron Sarcoplasmic Reticulum medicine.anatomical_structure chemistry Strontium Biophysics Electrophoresis Polyacrylamide Gel Calcium Channels Rabbits Adenosine triphosphate |
| Zdroj: | Canadian Journal of Physiology and Pharmacology. 70:394-402 |
| ISSN: | 1205-7541 0008-4212 |
| DOI: | 10.1139/y92-049 |
| Popis: | Sarcoplasmic reticulum (SR) vesicles, prepared from rabbit skeletal muscle, were characterized by functional and binding assays and incorporated into planar lipid bilayers. Single-channel activity was recorded in an asymmetric calcium buffer system and studied under voltage clamp conditions. Under these experimental conditions, a large conductance (100 pS in 50 mM Ca2+trans) divalent cation selective channel displaying high ruthenium red and low Ca2+ sensitivity was identified. This pathway has been previously described as the Ca2+-release channel of the SR of skeletal muscle. We now report that in the presence of a Mg–ATP complex, the Ca2+ sensitivity of the open probability of this channel is increased. Furthermore, we show that micromolar cis Sr2+ concentrations also activated the Ca2+-release channel. The open probability of the Sr2+-activated channel was increased in the presence of a 2 mM Mg–ATP complex and adenine nucleotides on the cytoplasmic face of the Ca2+-release channel. These results were confirmed by isotopic flux measurements using passively 45Ca2+-loaded vesicles. In the latter case, the presence of extra vesicular AMP-PCP (the nonhydroly sable ATP analog) enhanced the percentage of 45Ca2+ release induced either by Ca2+ or Sr2+ activation. In conclusion our findings emphasize the fact that the divalent cation activation of the Ca2+-release channel may be induced by Ca2+ and Sr2+, but not by Ba2+, in the presence of adenine nucleotides. Furthermore, they support the view that in situ Ca2+ and Mg–ATP complexes are involved in modulating the gating mechanism of this specific pathway.Key words: Ca2+ release, sarcoplasmic reticulum, planar lipid bilayer, strontium. |
| Databáze: | OpenAIRE |
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