title: Effects of erythropoietin on systemic hematocrit and oxygen transport in the splenectomized horse.
abstract: To test the hypotheses that erythropoietin (rhuEPO) treatment increases systemic hematocrit, maximal O2 uptake (VO2max, by elevated perfusive and diffusive O2 conductances) and performance five female horses (4-13 years) received 15 IU/kg rhuEPO (erythropoietin) three times per week for three weeks. These horses had been splenectomized over 1 year previously to avoid confounding effects from the mobilization of splenic red blood cell reserves. Each horse performed three maximal exercise tests (one per month) on an inclined (4°) treadmill to the limit of tolerance; two control trials and one following EPO treatment. Measurements of hemoglobin concentration ([Hb] and hematocrit), plasma and blood volume, VO2, cardiac output as well as arterial and mixed venous blood gases were made at rest and during maximal exercise. EPO increased resting [Hb] by 18% from 13.3 ± 0.6 to 15.7 ± 0.8 g/dL (mean ± SD) corresponding to an increased hematocrit from 36 ± 2 to 46 ± 2% concurrent with 23 and 10% reductions in plasma and blood volume, respectively (all P<0.05). EPO elevated VO2max by 20% from 25.7 ± 1.7 to 30.9 ± 3.4 L/min (P<0.05) via a 17% increase in arterial O2 content and 18% greater arteriovenous O2 difference in the face of an unchanged cardiac output. To achieve the greater VO2max after EPO, diffusive O2 conductance increased ∼ 30% (from 580 ± 76 to 752 ± 166 mL O2/mmHg/min, P<0.05) which was substantially greater than the elevation of perfusive O2 conductance. These effects of EPO were associated with an increased exercise performance (total running time: control, 216 ± 72; EPO, 264 ± 48 s, P<0.05). We conclude that EPO substantially increases VO2max and performance in the splenectomized horse via improved perfusive and diffusive O2 transport.
authors: Department of Animal Science, Rutgers the State University of New Jersey, New Brunswick, NJ 08903, United States. Electronic address: mckeever@aesop.rutgers.edu.
authors: Kenneth H
authors: KH
authors: McKeever
authors: School of Health, Physical Education and Recreation, The Ohio State University, Columbus, OH 43210, United States.
authors: Beth A
authors: BA
authors: McNally
authors: Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Melbourne, Australia.
authors: Kenneth W
authors: KW
authors: Hinchcliff
authors: Department of Kinesiology, University of Maine, Orono, ME, United States.
authors: Robert A
authors: RA
authors: Lehnhard
authors: Department of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University, United States.
authors: David C
authors: DC
authors: Poole
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis; D001809:Blood Viscosity / Q000502:physiology; D004921:Erythropoietin / Q000378:metabolism*; D005080:Exercise Test; D005260:Female; D006400:Hematocrit; D006439:Hemodynamics; D006454:Hemoglobins / Q000378:metabolism; D006736:Horses; D009068:Movement / Q000502:physiology; D010100:Oxygen / Q000378:metabolism*; D013156:Splenectomy
chemical_list: D006454:Hemoglobins; D004921:Erythropoietin; D010100:Oxygen
keywords: Arteriovenous O(2) difference; Cardiac output; Maximal aerobic capacity; Perfusive and diffusive O(2) transport