Defense Date

2010

Document Type

Thesis

Degree Name

Master of Science

Department

Physiology

First Advisor

Roland Pittman

Abstract

The endothelial glycocalyx plays an important role as part of the permeability barrier between the blood and the interstitium. In this study, we used different sized fluorescently labeled dextran molecules to determine the size of the macromolecular exclusion zone in capillaries. The width of the exclusion zone was calculated as one half the difference between the anatomic luminal diameter, as determined by transillumination, and the width of a fluorescent dextran column. During the first hour after systemic injection of labeled dextrans, neither 70 kDa dextran (Dextran 70) nor 500 kDa dextran (Dextran 500) labeled with the anionic fluorescein isothiocyanate (FITC) penetrated the endothelial glycocalyx to the endothelial cell surface. However, the 40 kDa dextran (Dextran 40) labeled with the neutral fluorophore Texas Red was able to penetrate to the endothelial cell surface. Under these control conditions, the width of the exclusion zone for Dextran 500 was 0.55 ± 0.02 mm (n=46); for Dextran 70 it was 0.50 ± 0.01 mm (n=111); and for Dextran 40 it was 0.08 ± 0.01 mm (n=53). One hour after systemically injecting the enzyme hyaluronidase, measurements of the exclusion zone were made using Dextrans 40, 70 and 500. After the enzyme treatment, Dextran 70 appeared to penetrate the glycocalyx layer, whereas Dextran 500 did not. Following hyaluronidase treatment, the width of the exclusion zone for Dextran 500 was 0.56 ± 0.02 mm (n=71); for Dextran 70 it was 0.05 ± 0.01 mm (n=103); and for Dextran 40 it was 0.03 ± 0.01 mm (n=33). These results indicate that the enzyme hyaluronidase was able to degrade the structural integrity of the glycocalyx, since after enzymatic treatment Dextran 70 was able to permeate the glycocalyx layer, while it was unable to prior to this treatment. However, the glycocalyx barrier was not completely compromised following hyaluronidase treatment since Dextran 500 still was not able to permeate the exclusion zone. In conclusion, macromolecules with 5.3 nm or larger radii will more than likely not be able to permeate an intact glycocalyx; in addition, degradation of hyaluronan will increase the permeability of the glycocalyx so that macromolecules with 5.3 nm radii will permeate.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

May 2010

Included in

Physiology Commons

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