Control of dual isoforms of Ca2+ release channels in muscle
Biol. Res
;
37(4): 583-591, 2004. ilus, tab, graf
Article
Dans Anglais
| LILACS
| ID: lil-437512
ABSTRACT
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.
Texte intégral:
Disponible
Indice:
LILAS (Amériques)
Sujet Principal:
Réticulum sarcoplasmique
/
Calcium
/
Canal de libération du calcium du récepteur à la ryanodine
/
Contraction musculaire
Type d'étude:
Étude pronostique
Limites du sujet:
Animaux
langue:
Anglais
Texte intégral:
Biol. Res
Thème du journal:
Biologie
Année:
2004
Type:
Article
Pays d'affiliation:
États-Unis d'Amérique
Institution/Pays d'affiliation:
Rush University Chicago/US
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