Increased SLC7A8 expression mediates L-DOPA uptake by renal tubular epithelial cells

The kidney serves a central role in the control of blood pressure through the release of vasoactive substances and the urinary excretion of Na+. Patients with essential hypertension usually exhibit persistent high blood pressure accompanied by Na+ retention. L-dihydroxyphenylalanine (L‑DOPA) is an amino acid, converted by the enzyme aromatic L‑amino acid decarboxylase to dopamine. The uptake of L‑DOPA by cells of the proximal tubular epithelium of the kidney is controlled by the L‑type amino acid transporter 2 (LAT2). LAT2 belongs to the solute carrier family 7 (SLC7) of amino acid transporters and is coded by the SLC7A8 gene. SLC7A8 expression is increased in the second‑order mesenteric arteries and kidneys of spontaneously hypertensive rats. The present study aimed to investigate the physiological role of the SLC7A8 gene in L‑DOPA handling by kidney cells. Selective upregulation of SLC7A8 mRNA and protein levels was achieved by adenoviral transduction of NRK‑52E cells, which retain several properties of proximal tubular epithelial cells. In addition, L‑DOPA uptake was determined using high performance liquid chromatography; NRK‑52E cells expressing SLC7A8 exhibited increased uptake of L‑DOPA. The results of the present study suggested that SLC7A8 may serve a critical role in blood pressure control through regulating L‑DOPA uptake in renal epithelial cells of the proximal tubule.