title: Elevation of organ resistance due to leukocyte perfusion.
abstract: Leukocytes are larger and considerably less deformable than erythrocytes, thereby causing a disproportionate effect on local blood flow, which despite their low concentration, may be significant at the organ level. To investigate the degree to which circulating leukocytes affect whole organ resistance, a hemodynamically isolated rat gracilis muscle was perfused in situ under well-controlled conditions. Comparison of organ pressure-flow data from vasodilated vasculature using normal physiological cell concentrations and perfusion pressures indicates that leukocytes (60-75% neutrophils) provide approximately 22% of the whole blood resistance despite their relatively small cell volume fraction of approximately 0.1%. On a single cell basis, each leukocyte imposes a resistance elevation equivalent to that of approximately 750 erythrocytes. Furthermore, when leukocytes are activated via pretreatment using N-formyl-methionyl-leucyl-phenylalanine or endotoxin, they show a higher resistance, accounting for 50-60% of the total resistance. These findings indicate that leukocytes play a significant role in normal skeletal muscle organ perfusion and may be a major determinant of organ perfusion during disease states.
authors.affiliation: Institute for Biomedical Engineering, University of California, San Diego, La Jolla 92093-0412.
authors.forename: D W
authors.initials: DW
authors.lastname: Sutton
authors.forename: G W
authors.initials: GW
authors.lastname: Schmid-Schönbein
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002196:Capillaries / Q000502:physiology; D004731:Endotoxins / Q000494:pharmacology; D004912:Erythrocytes / Q000502:physiology; D007962:Leukocytes / Q000187:drug effects / Q000502:physiology*; D009132:Muscles / Q000098:blood supply*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D010477:Perfusion; D051381:Rats; D011921:Rats, Inbred WKY; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance
chemical_list: D004731:Endotoxins; D009240:N-Formylmethionine Leucyl-Phenylalanine