title: Osmotic pressure exerted by entangled polysaccharide chains.
abstract: The osmotic behavior of neutral and charged polysaccharide chains was studied utilizing membrane osmometry. Two neutral dextran fractions characterized by weight-average molecular weights of 5 X 10(5) and 2 X 10(6) daltons yielded identical osmotic pressure (pi)--mass concentration (C) relationships in the range of 0 to 8 g/dl. Furthermore, the relations were highly non-linear and departed markedly from the ideal Van't Hoff equation. For hyaluronate characterized by a weight-average molecular weight of 2 X 10(6) daltons, the pi vs C relations were dependent on the electrolyte (NaCl) concentration of the solution. In the polymer concentration range of 0.5 to 1 g/dl, increasing the ionic strength from 0.15 to 2 M NaCl caused a reduction in oncotic activity. At lower hyaluronate concentrations, oncotic activity was not altered by neutralizing the anionic sites with excess NaCl. The non-ideal behavior of the neutral and charged polysaccharide chains are compatible with recent statistical thermodynamic analyses of oncotic activity in concentrated polymer solutions. Finally, nonlinear pi vs C relationships of the matrix biopolymers provide a sensitive mechanism for volume buffering in the interstitium.
mesh_terms: D002463:Cell Membrane Permeability / Q000187:drug effects; D003911:Dextrans / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006820:Hyaluronic Acid / Q000494:pharmacology; D008433:Mathematics; D008970:Molecular Weight; D009997:Osmotic Pressure; D011108:Polymers / Q000494:pharmacology / Q000502:physiology; D011134:Polysaccharides / Q000494:pharmacology*; D013223:Statistics as Topic; D013816:Thermodynamics
chemical_list: D003911:Dextrans; D011108:Polymers; D011134:Polysaccharides; D006820:Hyaluronic Acid