The tryptophan metabolite kynurenic acid (KYNA) plays a vital role in brain health as it provides neuroprotection (Schwarcz et al., 2012). Once synthesized in astrocytes from L-kynurenine (L-KYN) KYNA is released into the synaptic cleft to modulate release and effect of glutamate. However, transporters for L-KYN and KYNA in astrocytes have not been identified yet. Uric acid is a purine metabolite that is neuroprotective and connected to the tryptophan metabolism. Our aim was to identify the transporters for L-KYN and KYNA in human astrocytes and to investigate their regulation by uric acid. U373MG and primary human astrocytes (NHA) were used to examine expression of candidates for the two unidentified transporters such as BOCT1, many urate or known renal KYNA transporters such as OAT1 (Bahn et al., 2005), OAT3, URAT1, OAT4, OAT2, LAT1, GLUT9 or MRP4 by q-PCR and western blot analyses. We performed siRNA knock-down, uptake and efflux studies over 5 minutes at 37ᵒC with [3H]-KYNA or [3H]-KYN and suitable inhibitors such as L-leucin or MK-571 to identify the transporters for L-KYN and KYNA. The influence of urate (500µM) and L-KYN (1.5mM) on expression of all candidate transporters as well as KATII and EAAT1 were tested. Uptake of 25nM [3H]-KYN into U373MG and NHA cells was inhibited by 1mM of L-leucin down to 34% and 9%, respectively, indicating involvement of L-amino acid transporter 1 (LAT1). This was further examined by siRNA knock-down of LAT1 in U373MG and NHA cells, leading to a reduction of [3H]-KYN uptake by 47% and 27%. qPCR and western blot analyses confirmed LAT1 as the L-KYN uptake transporter in human astrocytes. To identify the efflux transporter for KYNA we screened U373MG and NHA cells by qPCR for possible candidates, revealing BOCT1, MRP4 and OAT1, of which only BOCT1 and MRP4 could be confirmed by western blot. Efflux of KYNA could be inhibited by MK-571 down to 50%, indicating that MRP4 may be the KYNA efflux transporter. Further siRNA studies are underway to confirm this finding. To evaluate the impact of urate on the kynurenine pathway, we incubated U373MG and NHA cells with urate (500µM) or L-kynurenine (1.5mM) and performed qPCR analysis. Interestingly, none of the tested proteins (LAT1, BOCT1, MRP4, VGLUT1, KATII or GLUT9) were regulated by urate. In summary, we have identified LAT1 as L-KYN uptake transporter in human astrocytes. Moreover, we have characterised possible KYNA efflux transporters and postulate that MRP4 is the KYNA efflux mechanism. The impact of urate on the kynurenine pathway is still open. Identification of the L-KYN and KYNA transporter paves the way for further understanding of diseases such as schizophrenia, Huntington or Alzheimer’s disease, in which KYNA levels in the brain are disturbed.