Dietz T H, Byrne R A, Lynn J W, Silverman H
Department of Zoology and Physiology, Louisiana State University, Baton Rouge 70803, USA.
Am J Physiol. 1995 Aug;269(2 Pt 2):R300-7. doi: 10.1152/ajpregu.1995.269.2.R300.
A hyperosmotic solution of mannitol or glucose (100 mM) in pond water caused an increase in paracellular solute movement between the bathing medium and body fluids of Dreissena polymorpha. Small molecules (< 5,000 Da) in the bath entered the mussel, and 80-85% of the sodium and chloride in the blood was lost within 12 h. Blood total solute was elevated within 4 h of exposure to hyperosmotic conditions, but the rise was attributed to the gain of glucose or mannitol from the bath and not to an elevation of ion concentration as a result of the osmotic loss of water. Lanthanum in the bathing solution was able to penetrate the paracellular junctional complex between gill epithelial cells in mussels exposed to hyperosmotic conditions but was rarely observed in pond water-acclimated animals. Colloidal gold (6 nm diam) was unable to penetrate the paracellular space but was accumulated in endocytotic vesicles in many epithelial cells. The "leakiness" of the epithelial tissue may be a critical factor in the low blood solute concentrations in freshwater mussels despite high rates of ion transport in these animals.
在池塘水中，甘露醇或葡萄糖（100 mM）的高渗溶液会导致多形饰贝（Dreissena polymorpha）的体表介质与体液之间的细胞旁溶质移动增加。浴液中的小分子（<5000 Da）进入贻贝，血液中80 - 85%的钠和氯在12小时内流失。暴露于高渗条件下4小时内，血液总溶质升高，但这种升高归因于从浴液中获得葡萄糖或甘露醇，而非因水的渗透流失导致离子浓度升高。在暴露于高渗条件的贻贝中，浴液中的镧能够穿透鳃上皮细胞之间的细胞旁连接复合体，但在适应池塘水的动物中很少观察到。直径6 nm的胶体金无法穿透细胞旁间隙，但在许多上皮细胞的内吞小泡中积累。尽管这些动物的离子转运速率很高，但上皮组织的“渗漏性”可能是淡水贻贝血液溶质浓度低的关键因素。
