Physiological Characterization of Density-Separated Thoroughbred Horse Erythrocytes

Abstract

To clarify the effects of free amino acid types on the change in the physiological character of equine erythrocytes with in vivo aging, the cell density, mean cell haemoglobin concentration (MCHC), acetylcholinesterase activity, osmotic fragility, alanine influx and reduced glutathione (GSH) content of the erythrocytes which were fractionated by the method of Murphy were compared among three types of horses which were classified according to the basic amino acid -positive (BA⁺) and -negative (BA^-), and GSH -low (GSH.L) and -high (GSH.H): type [BA⁺ :GSH.L] (I), [BA⁺ :GSH.H] (II) and [BA^-:GSH.H] (III) of erythrocytes. Except two of the type III animals, the cell density, MCHC, acetylcholinesterase activily and osmotic fragility of each cell population which was separated into six fractions based on density did not differ significantly among the three cell types. The increase in cell density was associated with a progressive increase in MCHC, and with the decrease in acetylcholinesterase activity and osmotic fragility. The osmotic fragilities of the above two type III were much higher than those of other horses, and did not differ among the six cell fractions. The alanine influx and GSH content of each fractionated cell showed significant differences among the three cell types. The ranking for alanine influx was type I < II < III, and that for GSH content was type I < II =(nearly equal) III. Increase in cell density was associated with a progressive decrease in the alanine influx of both types II and III, but not type I, and a decrease in GSH content in all three types of cells. These experimental results suggest that an increase in equine erythroid density is a function of their in vivo aging, regardless of the three cell types defined by BA and GSH systems. Moreover, the variation in alanine influx and GSH content in erythrocytes among the three cell types might take place before the release of mature red cells from the bone marrow into the circulation.