Species differences of galactose metabolism in erythrocytes

Galactose metabolism was studied in suspensions of erythrocytes from man, rat, ox and pig at approximate steady-state galactose concentrations from 0.1-6.5 mmol/l. There was no detectable galactose elimination in pig erythrocytes. In the three other species the elimination followed saturation kinetics with the maximal elimination rate, Vmax, being 8.0 mumol . min-1 . l-1 human erythrocytes; 12 mumol X min-1 . l-1 rat erythrocytes; 2.4 mumol . min-1 . l-1 bovine erythrocytes. The half saturation concentration, Km, was about the same in all three species, around 0.2 mmol/l. If similar in vivo, erythrocyte metabolism of galactose is not of major quantitative importance compared to the hepatic metabolism in the species examined.