ALPHA-KETOGLUTARATE UPTAKE IN HUMAN FIBROBLASTS

Glutamine requirements are increased during injury, in particular to s ustain the needs of rapidly growing cells. This includes fibroblasts i nvolved in wound healing. alpha-Ketoglutarate (alpha-KG) has been prov ed to be a potent precursor of glutamine. However, little is known abo ut the process of its cell uptake. Since this first step could be cruc ial in alpha-KG metabolism, we have characterized alpha-ketoglutarate uptake in fibroblasts. Total uptake of alpha-ketoglutarate was linear up to 1 mmol and temperature independent. Rate of uptake was independe nt of the presence of Na+ in the medium. Competition studies with anot her ketoacid demonstrated the nonspecificity of alpha-ketoglutarate up take. In addition, 4-hydroxy-alpha-cyanocinnamate, a known inhibitor o f anion transport, was ineffective on alpha-ketoglutarate uptake. Take n as a whole, these data provide evidence that alpha-ketoglutarate upt ake in fibroblast occurs by an unmediated diffusion process. This sugg ests that alpha-ketoglutarate uptake is not the controlling step in fi broblasts, i.e, only the availability of extracellular alpha-ketogluta rate. This could be an advantage since during injury, cell membrane de polarization and dissipation of Na+ gradient may limit cellular glutam ine uptake. (C) 1996 Academic Press Limited