LYSINE AND GLUTAMATE TRANSPORT IN THE ERYTHROCYTES OF COMMON BRUSHTAIL POSSUM, TAMMAR WALLABY AND EASTERN GREY-KANGAROO

It was recently coincidentally discovered, using H-1 NMR spectroscopy, that the erythrocytes of two species of Australian marsupials, Tammar Wallaby (Macropus eugenii) and Bettong (Bettongia penicillata), conta in relatively high concentrations of the essential amino acid lysine ( Agar NS, Rae CD, Chapman BE, Kuchel PW. Comp Biochem Physiol 1991;99B: 575-97). Hence, in the present work the rates of transport of lysine i nto the erythrocytes from the Common Brushtail Possum (Dactylopsila tr ivirgata) and Eastern Grey Kangaroo (Macropus giganteus) (which both h ave low lysine concentrations), and Tammar Wallaby were studied, to ex plore the mechanistic basis of this finding. The concentration-depende nce of the uptake was studied with lysine alone and in the presence of arginine, which may be a competitor of the transport in some species. In relation to GSH metabolism, glutamate uptake was determined in the presence and absence of Na+. The data was analysed to yield estimates of the maximal velocity (V-max) and the K-m in each of the species. E rythrocytes from Tammar Wallaby lacked saturable lysine transport in c ontrast to the other two species. The glutamate uptake was normal in a ll three animals for adequate GSH biosynthesis. (C) 1998 Elsevier Scie nce Inc. All rights reserved.