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This Article Full Text Full Text (PDF) All Versions of this Article: 569/2/631    most recent jphysiol.2005.096792v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Wiig, H. Articles by Bert, t. l. J. L. Search for Related Content PubMed PubMed Citation Articles by Wiig, H. Articles by Bert, t. l. J. L. Related Collections Cardiovascular

¹ Department of Biomedicine, University of Bergen, Norway
² Department of Chemical Engineering, University of British Columbia, Canada

At physiological pH, negatively charged glycosaminoglycans in the extracellular matrix may influence distribution volume of macromolecular probes, a phenomenon of importance for hydration of the interstitium and therefore for body fluid balance. We hypothesized that such charge effect was dependent on hydration. Human serum albumin (HSA) (the pH value for the isoelectric point (pI) = 4.9) was made neutral by cationization (cHSA) (pI = 7.6). Rat dermis was studied in vitro in a specially designed equilibration cell allowing control of hydration. Using a buffer containing labelled native HSA and cHSA, the distribution volumes were calculated relative to that of ⁵¹Cr-EDTA, an extracellular tracer. During changes in hydration (H), defined as (wet weight – dry weight) (dry weight)^–1), the slope of the equation describing the relationship between extracellular fluid volume (V_x) (in g H₂O (g dry weight)^–1) and H (V_x= 0.925 H + 0.105) differed significantly from that for available volumes of cHSA (V_a,cHSA= 0.624 H – 0.538) and HSA (V_a,HSA= 0.518 H – 0.518). A gradual reduction in H led to a reduction in difference between available volumes for the two albumin species. Screening the fixed charges by 1 M NaCl resulted in similar available and excluded volumes of native HSA and neutral cHSA. We conclude that during gradual dehydration, there is a reduced effect of fixed negative charges on interstitial exclusion of charged macromolecules. This effect may be explained by a reduced hydration domain surrounding tissue and probe macromolecules in conditions of increased electrostatic interactions. Furthermore, screening of negative charges suggested that hyaluronan associated with collagen may influence intrafibrillar volume of collagen and thereby available and excluded volume fraction.

(Received 17 August 2005; accepted after revision 6 October 2005; first published online 6 October 2005)
Corresponding author H. Wiig: Department of Biomedicine, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway. Email: helge.wiig{at}biomed.uib.no