Ca2+ 'sparks' and waves in intact ventricular muscle resolved by confocal imaging.
Ca2+ 'sparks' and waves in intact ventricular muscle resolved by confocal imaging.
复制标题
通过共焦成像解析完整心室肌中的 Ca2“火花”和波。
DOI：
10.1161/01.res.81.4.462
复制
发表时间：
1997
影响因子：
20.1
通讯作者：
Balke,CW
中科院分区：
文献类型：
--
作者：
Wier,WG;terKeurs,HE;Marban,E;Gao,WD;Balke,CW
The [Ca2+]itransient in heart is now thought to involve the recruitment and summation of discrete and independent “units” of Ca2+release (Ca2+“sparks”) from the sarcoplasmic reticulum, each of which is controlled locally by single coassociated L-type Ca2+channels (“local control theory of excitation-contraction coupling”). All prior studies on Ca2+sparks, however, have been performed in single enzymatically dissociated heart cells under nonphysiological conditions. In order to understand the possible significance of Ca2+sparks to normal working cardiac muscle, we used confocal microscopy to record Ca2+sparks, which are spatially averaged [Ca2+]itransients (and Ca2+waves), in individual cells of intact rat right ventricular trabeculae (composed of <15 cells in cross section) microinjected with the Ca2+indicator fluo 3 under physiological conditions ([Ca2+]o, 1 mmol/L; temperature, 33±1°C). Twitch force was recorded simultaneously. When stretched to optimal length (sarcomere length, 2.2 μm) and stimulated at 0.2 Hz, the trabeculae generated ≈700 μg of force per cell. Spatially averaged [Ca2+]itransients recorded from individual cells within a trabecula were similar to those recorded previously from single cells. The amplitude distribution of the peak ratio of Ca2+sparks was bimodal, with maxima at ratios of 1.8±0.3 and 2.7±0.2 (mean±SD), respectively. The amplitude of the peak of Ca2+sparks was ≈170 nmol/L. Ca2+sparks occurred at a frequency of 12.0±0.8/s (mean±SEM) in line scans covering 94 sarcomeres. Ca2+waves occurred randomly at a frequency of 0.57±0.08/s and propagated with a velocity of 29.5±1.7 μm/s. The extent of Ca2+wave propagation was 3.9±0.3 sarcomere lengths (sarcomere length, 2.2 μm). Ca2+sparks could be identified along the leading edge of the waves at intervals of 1.30±0.11 sarcomere length. Our observations suggest that (1) Ca2+sparks, similar to those recorded in single cells, occur in trabeculae under physiological conditions and (2) coupling of Ca2+spark generation between neighboring sites occurs and may lead to (3) the development of Ca2+waves, which propagate under physiological conditions at a low velocity over limited distances. The results suggest that concepts of excitation-contraction coupling recently derived from isolated myocytes are applicable to intact cardiac trabeculae.
