Physiological function of free D-alanine as an iso-osmotic effector in crustaceans

游离 D-丙氨酸作为甲壳类动物等渗效应物的生理功能

• 批准号: 07660278
• 负责人: ABE Hiroki
• 金额: $ 1.6万
• 依托单位: Kyoritsu Women's University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07660278/
• 关键词: iso-osmotic regulation; crustacean; D-alanine; D-amino acid; hyper-osmosis; free amino acid

Free D- and L-amino acids were determined on the various tissues of crayfish Porcambarus clarkii, marsh crab Holometopus dehaani, and shore crab Hemigrapsus penicillatus during seawater acclimation from freshwater.Along with the hyper-osmotic stress, several free amino acids increased in the muscle as well as the other tissues of these crustaceans. Of several D-amino acids found in the tissues, only D-alanine increased significantly during seawater acclimation. The ratio of D-alanine to total alanine also increased to about 50% in seawater. These data clearly indicate that D-alanine is a major osmo-effector for maintaining the tissue iso-osmotic pressure in these crustaceans.Woolly-handed crab Eriocheir japonicus, which migrates downstream during spawning in fall, did not show clear increase of free amino acids and D-alanine during seawater acclimation before summer. D-Alanine in the tissues of this crab is much higher in the individuals obtained from summer to fall than those from spring to summer. During seawater acclimation of this species obtained after summer, the increase of D-alanine was high and reached to almost the same level as that in naturally migrated individuals captured at seashore. During seawater acclimation, hemolymph showed the increase of only inorganic ions and no change of free amino acids and betaines. Thus, these data indicate that only inorganic ions are responsible for the osmotic regulation in hemolymph but D-alanine as well as other several amino acids are also responsible up to 45% of total osmolytes for the tissue iso-osmotic regulation of this species during downstream spawning migration.In this study, the physiological function of D-alanine in the tissues of crustaceans was elucidated to be as a major iso-osmotic effector. The level of D-alanine in the muscle of crayfish was also known to be maintained even after starvation in seawater and after administration of D- or L-alanine in the muscle.

在淡水驯化期间，对克氏小龙虾、沼泽蟹 Holometopus dehaani 和岸蟹 Hemigrapsus penicillatus 的各种组织中的游离 D- 和 L- 氨基酸进行了测定。随着高渗透压，一些游离氨基酸在淡水驯化过程中增加。这些甲壳类动物的肌肉以及其他组织。在组织中发现的几种 D-氨基酸中，只有 D-丙氨酸在海水适应过程中显着增加。海水中D-丙氨酸占总丙氨酸的比例也增加到50%左右。这些数据清楚地表明，D-丙氨酸是维持这些甲壳类动物组织等渗压的主要渗透效应物。毛手蟹在秋季产卵期间向下游迁移，没有显示出游离氨基酸的明显增加和夏季前海水驯化过程中的D-丙氨酸。夏季至秋季获得的螃蟹组织中的 D-丙氨酸含量远高于春季至夏季获得的个体。该物种在夏季后进行的海水驯化过程中，D-丙氨酸的增加量很高，几乎与在海边捕获的自然迁徙个体相同的水平。在海水驯化过程中，血淋巴仅显示无机离子增加，游离氨基酸和甜菜碱没有变化。因此，这些数据表明，只有无机离子负责血淋巴中的渗透调节，但 D-丙氨酸以及其他几种氨基酸也负责该物种下游过程中组织等渗调节的总渗透剂的 45%。在这项研究中，D-丙氨酸在甲壳类动物组织中的生理功能被阐明为主要的等渗效应物。众所周知，即使在海水中饥饿后以及在肌肉中施用 D- 或 L-丙氨酸后，小龙虾肌肉中的 D-丙氨酸水平也能保持不变。