title: Hepatic blood flow in horses during the recuperative period from maximal exercise.
abstract: OBJECTIVE
  To determine effects of walking or standing on hepatic blood flow of horses after brief, intense exercise.
  
  
  METHODS
  6 adult Thoroughbreds (4 mares, 2 geldings).
  
  
  METHODS
  Horses were preconditioned on a treadmill to establish uniform level of fitness. Once fit, treadmill speed causing each horse to exercise at 120% of maximal oxygen consumption was determined and used in simulated races at 14-day intervals. In a three-way crossover study, horses were exercised at a speed inducing 120% of maximal oxygen consumption until fatigued or for a maximum of 2 minutes. Three interventions were studied: resting on the treadmill (REST), exercised then standing on the treadmill for 30 minutes (MS), and exercised then walking at 2 m/s for 30 minutes (MW). At 60 seconds after completion of exercise, bromsulphalein (BSP) was infused IV, and blood samples were collected every 2 minutes for 30 minutes for analysis of BSP concentration. Hematocrit and plasma total solids concentration were measured. Pharmacokinetic parameters were derived, using nonlinear regression, and were compared, using Friedman's repeated measures analysis on ranks.
  
  
  RESULTS
  Plasma BSP concentration was higher after exercise. Median hepatic blood flow (BSP clearance) decreased significantly from 23.8 (REST) to 20.7 (MS) and 18.7 (MW) ml/min/kg. Median steady-state volume of distribution of BSP decreased from 47.6 (REST) to 42.7 (MW) and 40.2 (MS) ml/kg. Differences among trials were not significant when horses walked or stood after exercise.
  
  
  CONCLUSIONS
  Hepatic blood flow and pharmacokinetics of BSP are markedly altered immediately after exercise. Limiting movement of horses during this period did not affect hepatic blood flow.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus 43210-1089, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Dyke
authors.forename: J A
authors.initials: JA
authors.lastname: Hubbell
authors.forename: R A
authors.initials: RA
authors.lastname: Sams
authors.forename: K W
authors.initials: KW
authors.lastname: Hinchcliff
mesh_terms: D000818:Animals; D018592:Cross-Over Studies; D005080:Exercise Test / Q000662:veterinary; D005260:Female; D006400:Hematocrit; D006736:Horses / Q000097:blood / Q000502:physiology*; D007202:Indicators and Reagents / Q000493:pharmacokinetics; D008099:Liver / Q000378:metabolism; D008102:Liver Circulation / Q000502:physiology*; D008297:Male; D008657:Metabolic Clearance Rate / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013448:Sulfobromophthalein / Q000493:pharmacokinetics
chemical_list: D007202:Indicators and Reagents; D013448:Sulfobromophthalein