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Open Access Research article

Plasma proteins in a standardised skin mini-erosion (II): effects of extraction pressure

Christer Svedman1*, Bing B Yu2, Terence J Ryan3 and Henry Svensson4

Author Affiliations

1 Department of Plastic and Reconstructive Surgery, Malmö University Hospital, University of Lund, Lund, Sweden

2 Department of Biochemistry, University of Oxford, Oxford, UK

3 Department of Dermatology, Churchill Hospital, Oxford, UK

4 Department of Plastic and Reconstructive Surgery, Malmö University Hospital, University of Lund, Lund, Sweden

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BMC Dermatology 2002, 2:4  doi:10.1186/1471-5945-2-4

Published: 11 February 2002

Abstract

Background

A standardised suction technique has been used to sample plasma proteins in dermal interstitial fluid (IF) serially for 5 to 6 days from a suction-induced skin mini-erosion. Increased protein concentrations ascribed to inflammation have been shown from day 1 onward. In this study, we assessed the effect of two different extraction pressures on IF sample composition.

Methods

Total protein concentration and the concentrations of insulin, prealbumin, albumin, transferrin, IgG and alpha-2-macroglobulin were assessed daily in healthy volunteers. Samples were extracted at 50 mmHg and 200 mmHg below the atmospheric.

Results

At 0 h after forming the erosion, mean total IF protein content (relative to plasma) was lower in the samples extracted at -200 mmHg than at -50 mmHg (26 +/-13% (SD) vs 48 +/-9.8%; p < 0.05). There were no significant differences at 24, 48, 72 or 96 h. Of the individual proteins, expressed as area units (AU) for area under the curve (AUC) from 0–96 h, albumin was lower in IF sampled at -200 mmHg (2.49 +/- 0.68 vs 3.08 +/- 0.36 AU; p < 0.05), as was transferrin (1.91 +/- 0.52 vs 2.40 +/- 0.42 AU; p < 0.05). Extraction volumes were significantly higher at -200 mmHg (AUC diff: 60%; p < 0.05).

Conclusions

Samples of IF extracted at 0 h at -200 mmHg contained lower protein concentrations, indicating an increased water fraction and an intact sieve function of the vascular wall. The difference in protein concentration extracted at higher and lower pressure from 24 h onward was less pronounced. Lower pressure should be used to sample substances of greater molecular size.