Effects of exercise on erythrocytes in normal and splenectomised Thoroughbred horses

Abstract

SummaryChanges in erythrocyte quality during exercise were determined in 3 control (Group C) and 3 splenectomised (Group 5) horses that performed an incremental exercise test on a treadmill until the point of fatigue. Venous blood samples were drawn before the exercise test and immediately after warming‐up and incremental exercise test. Incremental exercise increased erythrocyte count and haemoglobin concentration by 46 and 37% respectively in control horses and by 15 and 17% respectively inGroup Sanimals. Packed cell volume (PCV) increased by 48% in controls but there was no change inGroup Sanimals. Warming‐up decreased mean cell volume (MCV), mean cell Hb (MCH) and mean cell Hb concentration (MCHC) by 9, 19 and 7% in control horses. Incremental exercise restored MCV and MCHC but MCH remained lower than the resting level. InGroup Shorses, warming‐up and incremental exercise decreased MCV by 6 and 9% respectively, did not change MCH, but increased MCHC by 4 and 15% respectively. Incremental exercise increased erythrocyte density (ED) inGroup Cbut not inGroup Shorses. Osmotic fragility of erythrocytes measured as the red cell haemolysis rates in 0.56% NaCl (HL) were significantly higher inGroup Cthan inGroup Shorses regardless of exercise. Warming‐up decreased HL by 7% inGroup Cvs 19% inGroup Shorses, but exercise increased HL by 26% inGroup Cvs 38% inGroup Shorses. These results suggest that: 1) exercise causes shrinking of erythrocytes; 2) erythrocyte indices are dependent on the intensity of the exercise; 3) release of erythrocytes from the spleen is associated with an increase in osmotic fragility; and 4) exercise changes osmotic fragility regardless of the release of erythrocytes from the spleen into circulation.