The effect of training and physical exercise on the energetic metabolism of equine erythrocytes.

Abstract: Erythrocytes, due to their simple metabolic processes, differ greatly from nucleated cells. Their main metabolite of glycolysis is 2,3-Diphosphoglycerate (2,3-DPG), which serves also as an energy store for producing ATP in the pyruvate kinase reaction. 2,3-DPG modifies also the affinity of haemoglobin for oxygen (4). Increase in the concentration of 2,3-DPG, ATP and body temperature, or a decrease in the pH value of blood causes decreased affinity of haemoglobin for oxygen as blood transverses muscle capillaries, facilitating oxygen delivery. In equine erythrocytes, the level of ATP is severalfold lower than in human erythrocytes despite the fact that the consumption of glucose, as well as the concentration of 2,3-DPG in red blood cells in these species, is similar. It is well known that physical effort causes a rise in haemoglobin concentration in the blood, without changing the mean corpuscular haemoglobin concentration. This effect is caused partly by loss of extracellular water (through the lungs and with sweat) and by water transfer to the tissues. These processes are associated with elevation of electrolyte content in plasma (9). On the other hand, in horses, physical exercise as well as stress factors cause release of erythrocytes from the spleen. Red blood cells stored in the spleen are contantly exchanged with circulating ones so there are no differences in their properties. It can be observed that intensive physical exercise can produce an increase of the haematocrit (Htc) value to above 65 YO (19). Analogius changes in the Htc value in man are less then those observed in horses and are more related to the physical condition of the organism than to the intensity of physical effort (10). During muscular activity, intensive release of lactic acid, uric acid and ammonia from muscle is observed (9, 15,19). In addition, some studies report changes in the insulin blood level and in sensitivity of erythrocytes to this hormone (6, 8). Thus, there is a close relationship between the metabolism of erythrocytes and the work of muscle despite the fact that the direction of changes in the energy level in these tissues may differ (12). The purpose of this study was to determine the influence of physical exercise and training on erythrocyte glucose utilization and also on the 2,3-DPG and ATP concentration in equine erythrocytes.