Abstract
We have examined the distribution of ryanodine receptors, L-type Ca$^2+$
channels, calsequestrin, Na$^+$/Ca$^2+$ exchangers, and voltage-gated
Na$^+$ channels in adult rat ventricular myocytes. Enzymatically
dissociated cells were fixed and dual-labeled with specific antibodies
using standard immunocytochemistry protocols. Images were deconvolved
to reverse the optical distortion produced by wide-field microscopes
equipped with high numerical aperture objectives. Every image showed
a well-ordered array of fluorescent spots, indicating that all of
the proteins examined were distributed in discrete clusters throughout
the cell. Mathematical analysis of the images revealed that dyads
contained only ryanodine receptors, L-type Ca$^2+$ channels,
and calsequestrin, and excluded Na$^+$/Ca$^2+$ exchangers
and voltage-gated Na$^+$ channels. The Na$^+$/Ca$^2+$
exchanger and voltage-gated Na$^+$ channels were distributed
largely within the t-tubules, on both transverse and axial elements,
but were not co-localized. The t-tubule can therefore be subdivided
into at least three structural domains; one of coupling (dyads),
one containing the Na$^+$/Ca$^2+$ exchanger, and one containing
voltage-gated Na$^+$ channels. We conclude that if either the
slip mode conductance of the Na$^+$ channel or the reverse mode
of the Na$^+$/Ca$^2+$ exchanger are to contribute to the
contractile force, the fuzzy space must extend outside of the dyad.
- (analysis),
- (genetics),
- 11053140
- 16,
- 18,
- adult,
- amniocentesis,
- and
- aneuploidy,
- animals,
- bandages,
- biopsy,
- britain,
- calcium
- calsequestrin,
- chain
- channel,
- channels,
- chromosome,
- chromosomes,
- computer-assisted,
- contraction,
- detection,
- determination
- diagnosis,
- embryo
- exchanger,
- female,
- fertilization
- fluorescence,
- fractions,
- genotype,
- gov't,
- great
- health
- heterozygote
- human,
- humans,
- hybridization,
- image
- in
- incontinentia
- injections,
- intracytoplasmic,
- karyotyping,
- l-type,
- linkage
- male,
- muscle
- myocardial
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