Studies on Changes in Toughness of the Body Wall from Sea Cucumber

海参的体壁会迅速改变其力学性能。然而，所涉及的机制还不完全清楚。本文研究了与酸性糖胺聚糖(AGAG)相关的海参体壁韧性的阳离子依赖性变化。刺参体壁在无盐条件下的韧性为0.6~1.4公斤，单价阳离子显著降低，在0.3M氯化钠或0.4M氯化钾时达到零。CaCl2和MgCl2的加入使韧性有下降的趋势，但幅度较小。在0.1M的氯化钠、氯化钾、氯化钙和氯化镁中，海参的比粘度(&lt；eta&gt；sp)分别从无盐时的0.7降至0.47、0.51、0.49和0.57。随着盐浓度的增加，一价阳离子的&lt；eta&gt；sp逐渐减少，而二价阳离子的&lt；eta&gt；sp值逐渐增加。化学分析表明，海参AGag中含有19%的葡萄糖醛酸、33%的N-乙酰半乳糖胺和30%的硫酸软骨素，表明其为硫酸软骨素。切片经柠檬酸铅染色后，电子显微镜下可见大量胶原纤维。通过对脱盐的体壁进行Ru红染色，发现AGAG分布在胶原纤维之间及其周围部分。Ru红染色观察到，氯化钠处理后的体壁出现了一定程度的凝聚。这些观察结果表明，AGAG在海参体壁韧性变化中起着重要作用。

Holothurian body wall rapidly changes its mechanical properties. However, the mechanisms involved are not fully understood. The present study deals with the cation-dependent changes in toughness of holothurian body wall in association with acidic glycosaminoglycan(AGAG).1. The toughness of the body wall from a sea cucumber Stichopus japonicus was 0.6 to 1.4kg in the absence of salt and decreased markedly by monovalent cations, until it reached zero at 0.3M NaCl or 0.4M KCl. The toughness tended to decrease by CaCl_2 and MgCl_2, though the extent was much smaller.2. The specific viscosity (<eta>sp) of holothurian AGAG decreased from 0.7 in the absence of salt to 0.47, 0.51, 0.49, and 0.57 in 0.1M NaCl, KCl, CaCl2, and MgCl_2, respectively. Increase of salt concentration resulted in a successive decrease of <eta>sp with monovalent cations, whereas <eta>sp rather increased with divalent cations.3. Chemical analyses showed that sea cucumber AGAG contained 19% glucuronic acid, 33% N-acetyl galactosamine and 30% SO^<4->, suggesting that it was a kind of chondroitin sulfate.4. Electron micrographs of the thin sections stained with lead citrate showed many collagen fibrils. By ruthenium red staining of the desalted body wall, AGAG was found to be distributed between collagen fibers and in their peripheral portions. When the body wall was treated with NaCl, there occurred some coagulation of thin fibrils as observed by ruthenium red staining.5. It was suggested from these observations that AGAG plays an important role in toughness changes of the body wall of sea cucumber.