title: Microvascular blood flow resistance: role of endothelial surface layer.
abstract: Observations of blood flow in microvascular networks have shown that the resistance to blood flow is about twice that expected from studies using narrow glass tubes. The goal of the present study was to test the hypothesis that a macromolecular layer (glycocalyx) lining the endothelial surface contributes to blood flow resistance. Changes in flow resistance in microvascular networks of the rat mesentery were observed with microinfusion of enzymes targeted at oligosaccharide side chains in the glycocalyx. Infusion of heparinase resulted in a sustained decrease in estimated flow resistance of 14-21%, hydrodynamically equivalent to a uniform increase of vessel diameter by approximately 1 micron. Infusion of neuraminidase led to accumulation of platelets on the endothelium and doubled flow resistance. Additional experiments in untreated vascular networks in which microvascular blood flow was reduced by partial microocclusion of the feeding arteriole showed a substantial increase of flow resistance at low flow rates (average capillary flow velocities < 100 diameters/s). These observations indicate that the glycocalyx has significant hemodynamic relevance that may increase at low flow rates, possibly because of a shear-dependent variation in glycocalyx thickness.
authors.affiliation: Department of Physiology, Freie Universität Berlin, Germany.
authors.forename: A R
authors.initials: AR
authors.lastname: Pries
authors.forename: T W
authors.initials: TW
authors.lastname: Secomb
authors.forename: H
authors.initials: H
authors.lastname: Jacobs
authors.forename: M
authors.initials: M
authors.lastname: Sperandio
authors.forename: K
authors.initials: K
authors.lastname: Osterloh
authors.forename: P
authors.initials: P
authors.lastname: Gaehtgens
mesh_terms: D000818:Animals; D001160:Arterioles / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure; D004730:Endothelium, Vascular / Q000502:physiology*; D019276:Glycocalyx; D019763:Heparin Lyase / Q000494:pharmacology; D008833:Microcirculation / Q000502:physiology*; D018715:Microscopy, Video / Q000379:methods; D008955:Models, Cardiovascular; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D051381:Rats; D013152:Splanchnic Circulation / Q000502:physiology; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D019763:Heparin Lyase