Cario C, Malaval L, Hernandez-Nicaise M L
Laboratoire de Physiologie Cellulaire et Moléculaire - URA CNRS 1938, Université de Nice-Sophia Antipolis, Parc Valrose, F-06108 Nice, France.
Cell Tissue Res. 1995 Dec;282(3):435-43. doi: 10.1007/BF00318875.
The sarcoplasmic reticulum has been studied in radial and longitudinal giant smooth muscle fibres of the marine planktonic invertebrate Beroe. Impregnation with heavy metals has revealed that the smooth component is organised in a longitudinally oriented three-dimensional network of tubules running along the myofilaments. An ultrastructural morphometric analysis has shown that the relative volume of the sarcoplasmic reticulum is the same (1% of the myofilament volume) in both fibres but that the size, number and distribution of the sarcoplasmic reticulum tubules differ significantly. The longitudinal fibres are characterised physiologically by an action potential with a short calcium-dependent plateau that can trigger a short contraction; radial fibres produce action potentials without a plateau and their contraction requires a train of spikes. The sarcoplasmic reticulum tubules in longitudinal fibres are thinner (132 nm in diameter) and more numerous than those in radial fibres (160 nm in diameter). Moreover, the tubules are homogeneously distributed among the myofilaments in radial fibres, whereas they are more numerous in the centre of longitudinal muscles.
对海洋浮游无脊椎动物海醋栗的径向和纵向巨大平滑肌纤维中的肌浆网进行了研究。用重金属浸染显示，平滑肌成分由沿着肌丝纵向排列的三维小管网络构成。超微结构形态计量分析表明，两种纤维中肌浆网的相对体积相同（占肌丝体积的1%），但肌浆网小管的大小、数量和分布存在显著差异。纵向纤维的生理特征是具有短钙依赖性平台期的动作电位，可引发短时间收缩；径向纤维产生无平台期的动作电位，其收缩需要一连串的尖峰电位。纵向纤维中的肌浆网小管比径向纤维中的更细（直径132纳米）且数量更多（径向纤维直径160纳米）。此外，小管在径向纤维的肌丝中均匀分布，而在纵向肌肉的中心则数量更多。
