α-KETOGLUTARATE UPTAKE IN HUMAN FIBROBLASTS

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Abstract

Glutamine requirements are increased during injury, in particular to sustain the needs of rapidly growing cells. This includes fibroblasts involved in wound healing. α-Ketoglutarate (α-KG) has been proved to be a potent precursor of glutamine. However, little is known about the process of its cell uptake. Since this first step could be crucial in α-KG metabolism, we have characterized α-ketoglutarate uptake in fibroblasts. Total uptake of α-ketoglutarate was linear up to 1mmol and temperature independent. Rate of uptake was independent of the presence of Na+in the medium. Competition studies with another ketoacid demonstrated the non-specificity of α-ketoglutarate uptake. In addition, 4-hydroxy-α-cyanocinnamate, a known inhibitor of anion transport, was ineffective on α-ketoglutarate uptake. Taken as a whole, these data provide evidence that α-ketoglutarate uptake in fibroblast occurs by an unmediated diffusion process. This suggests that α-ketoglutarate uptake is not the controlling step in fibroblasts, i.e. only the availability of extracellular α-ketoglutarate. This could be an advantage since during injury, cell membrane depolarization and dissipation of Na+gradient may limit cellular glutamine uptake.

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