title: Effects of hematocrit and erythrocyte deformability on pulmonary vascular pressures in perfused pony lungs.
abstract: OBJECTIVE
  To evaluate the contribution of hematocrit and RBC deformability to pulmonary vascular pressures of racehorses.
  
  
  METHODS
  Pony lungs were isolated and right and left lungs were perfused separately with blood. The effects of changing hematocrit and of pentoxifylline treatment were evaluated.
  
  
  METHODS
  11 healthy mixed-breed ponies.
  
  
  METHODS
  Ponies were anesthesized, blood was collected, and lungs were removed and perfused with blood at constant flow rate.
  
  
  RESULTS
  Increasing the hematocrit from 35% to 65% resulted in increases in pulmonary arterial pressure (53%, 45%), capillary shear stress (45%, 32%), and total vascular resistance (92%, 143%) at low (352 +/- 33 ml/min) and high (1,442 +/- 48 ml/min) flow rates, respectively. Pulmonary artery pressures were lower (10%, 11%) when lungs were perfused with blood from pentoxifylline-treated ponies, compared with blood from control ponies with low hematocrit (PCV, 30%) and low-flow rate and with high hematocrit (PCV, 45%) and high flow rate, respectively. Decreases in capillary shear stress and total vascular resistance were also observed for pentoxifylline-treated blood.
  
  
  CONCLUSIONS
  Increases in hematocrit equivalent to those occurring during competitive racing activity contribute substantially to pulmonary vascular pressures in horse lungs. Administration of pentoxifylline to ponies reduced RBC deformability and attenuated increases in pulmonary vascular pressures.
  
  
  CONCLUSIONS
  Treatment of racehorses with pentoxifylline may reduce exercise-associated increases in pulmonary vacular pressure, thereby attenuating exercise-induced pulmonary hemorrhage.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Weiss
authors.forename: K
authors.initials: K
authors.lastname: Richwagen
authors.forename: O A
authors.initials: OA
authors.lastname: Evanson
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002196:Capillaries / Q000502:physiology; D004907:Erythrocyte Deformability; D006400:Hematocrit; D006736:Horses / Q000502:physiology*; D066298:In Vitro Techniques; D008168:Lung / Q000098:blood supply*; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D010431:Pentoxifylline / Q000494:pharmacology; D010477:Perfusion; D011651:Pulmonary Artery / Q000502:physiology*; D011652:Pulmonary Circulation / Q000187:drug effects; D011667:Pulmonary Veins / Q000502:physiology; D014655:Vascular Resistance
chemical_list: D010431:Pentoxifylline