Control of dual isoforms of Ca2+ release channels in muscle
Here we compare excitation-contraction coupling in single muscle cells of frogs and rats. Because amphibians have isoform 3 (or b) of the ryanodine receptor/Ca2+ release channel, in addition to 1 (a), which is also present in the mammal, any extra feature present in the frog may in principle be attr...
Guardado en:
| Autores principales: | , |
|---|---|
| Lenguaje: | English |
| Publicado: |
Sociedad de Biología de Chile
2004
|
| Materias: | |
| Acceso en línea: | http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000400012 |
| Etiquetas: |
Agregar Etiqueta
Sin Etiquetas, Sea el primero en etiquetar este registro!
|
| Sumario: | Here we compare excitation-contraction coupling in single muscle cells of frogs and rats. Because amphibians have isoform 3 (or b) of the ryanodine receptor/Ca2+ release channel, in addition to 1 (a), which is also present in the mammal, any extra feature present in the frog may in principle be attributed to isoform 3. Ca2+ release under voltage clamp depolarization has a peak and a steady phase in both taxonomic classes, but the peak is more marked in the frog, where the ratio of amplitudes of the two phases is voltage-dependent. This dependence is a hallmark of CICR. Confocal imaging identified Ca2+ sparks in the frog, but not in the voltage-clamped rat cells. Because Ca2+ sparks involve CICR both observations indicate that the contribution of CICR is minor or null in the mammal. The "couplon" model well accounts for observations in the frog, but assumes a structure that we now know to be valid only for the rat. A revised model is proposed, whereby the isoform 3 channels, located parajunctionally, are activated by CICR and contribute its characteristic global and local features. Several issues regarding the roles of different channels remain open to further study. |
|---|