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Local calcium release in mammalian skeletal muscle.
Shirokova, N; García, J; Ríos, E.
Afiliação
  • Shirokova N; Department of Molecular Biophysics and Physiology, Rush University, 1750 W. Harrison Street, Chicago, IL 60612, USA. nshiroko@rush.edu
J Physiol ; 512 ( Pt 2): 377-84, 1998 Oct 15.
Article em En | MEDLINE | ID: mdl-9763628
1. Fluo-3 fluorescence associated with Ca2+ release was recorded with confocal microscopy in single muscle fibres mechanically dissected from fast twitch muscle of rats or frogs, voltage clamped in a two Vaseline-gap chamber. 2. Interventions that elicited Ca2+ sparks in frog skeletal muscle (low voltage depolarizations, application of caffeine) generated in rat fibres images consistent with substantial release from triadic regions, but devoid of resolvable discrete events. Ca2+ sparks were never observed in adult rat fibres. In contrast, sparks of standard morphology were abundant in myotubes from embryonic mice. 3. Depolarization-induced gradients of fluorescence between triadic and surrounding regions (which are proportional to Ca2+ release flux) peaked at about 20 ms and then decayed to a steady level. Gradients were greater in frog fibres than in rat fibres. The ratio of peak over steady gradient (R) was steeply voltage dependent in frogs, reaching a maximum of 4.8 at -50 mV (n = 7). In rats, R had an essentially voltage-independent value of 2.3 (n = 5). 4. Ca2+-induced Ca2+ release, resulting in concerted opening of several release channels, is thought to underlie Ca2+ sparks and the peak phase of release in frog skeletal muscle. A diffuse 'small event' release, similar to that observed in these rats, is also present in frogs and believed to be directly activated by voltage. The present results suggest that in these rat fibres there is little contribution by CICR to Ca2+ release triggered by depolarization, and a lack of concerted channel opening.
Assuntos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Cafeína / Cálcio / Músculo Esquelético / Fibras Musculares Esqueléticas / Sinalização do Cálcio Limite: Animals Idioma: En Revista: J Physiol Ano de publicação: 1998 Tipo de documento: Article País de afiliação: Estados Unidos País de publicação: Reino Unido

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Cafeína / Cálcio / Músculo Esquelético / Fibras Musculares Esqueléticas / Sinalização do Cálcio Limite: Animals Idioma: En Revista: J Physiol Ano de publicação: 1998 Tipo de documento: Article País de afiliação: Estados Unidos País de publicação: Reino Unido