GLUTAMINE TRANSPORT IN NORMAL AND ACIDOTIC RAT-KIDNEY MITOCHONDRIA

Glutamine transport in both normal and acidotic rat kidney mitochondri a was investigated using both isotopic techniques and by spectroscopic measurements in which glutamine metabolism was allowed to occur. Wide ly used criteria for demonstrating the occurrence of carrier-mediated transport were successfully applied in both cases. Three transport mec hanisms were found to occur, namely glutamine uniport, active only dur ing acidosis and glutamine/glutamate and glutamine/malate antiports, a ctive in both normal and acidotic mitochondria. Efflux of glutamate, v ia a glutamate/OH- translocator, following glutamine uptake by mitocho ndria was experimentally ruled out. Glutamine uniport in acidotic mito chondria and glutamine/glutamate and glutamine/malate antiports in bot h normal and acidotic mitochondria were investigated in detail: differ ences found in K-m and V-max values, in pH and temperature dependence, and in the pattern of inhibitor sensitivity of glutamine transport de monstrated the existence of five different translocators whose activit ies were found to fit with the physiological requirements of renal amm oniogenesis. (C) 1994 Academic Press, Inc.