Insulin-stimulated L-arginine transport requires SLC7A1 gene expression and is associated with human umbilical vein relaxation

J Cell Physiol. 2011 Nov;226(11):2916-24. doi: 10.1002/jcp.22635.


Insulin causes endothelium-derived nitric oxide (NO)-dependent vascular relaxation, and increases L-arginine transport via cationic amino acid transporter 1 (hCAT-1) and endothelial NO synthase (eNOS) expression and activity in human umbilical vein endothelium (HUVEC). We studied insulin effect on SLC7A1 gene (hCAT-1) expression and hCAT-transport activity role in insulin-modulated human fetal vascular reactivity. HUVEC were used for L-arginine transport and L-[(3) H]citrulline formation (NOS activity) assays in absence or presence of N-ethylmaleimide (NEM) or L-lysine (L-arginine transport inhibitors). hCAT-1 protein abundance was estimated by Western blot, mRNA quantification by real time PCR, and SLC7A1 promoter activity by Luciferase activity (-1,606 and -650 bp promoter fragments from ATG). Specific protein 1 (Sp1), and total or phosphorylated eNOS protein was determined by Western blot. Sp1 activity (at four sites between -177 and -105 bp from ATG) was assayed by chromatin immunoprecipitation (ChIP) and vascular reactivity in umbilical vein rings. Insulin increased hCATs-L-arginine transport, maximal transport capacity (V(max) /K(m) ), and hCAT-1 expression. NEM and L-lysine blocked L-arginine transport. In addition, it was trans-stimulated (∼7.8-fold) by L-lysine in absence of insulin, but unaltered (~1.4-fold) in presence of insulin. Sp1 nuclear protein abundance and binding to DNA, and SLC7A1 promoter activity was increased by insulin. Insulin increased NO synthesis and caused endothelium-dependent vessel relaxation and reduced U46619-induced contraction, effects blocked by NEM and L-lysine, and dependent on extracellular L-arginine. We suggest that insulin induces human umbilical vein relaxation by increasing HUVEC L-arginine transport via hCATs (likely hCAT-1) most likely requiring Sp1-activated SLC7A1 expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / pharmacology
  • Arginine / metabolism*
  • Biological Transport / drug effects
  • Cationic Amino Acid Transporter 1 / genetics*
  • Cells, Cultured
  • Endothelial Cells / metabolism
  • Enzyme Inhibitors / pharmacology
  • Ethylmaleimide / pharmacology
  • Female
  • Gene Expression*
  • Humans
  • Insulin / metabolism*
  • Insulin / pharmacology
  • Lysine / pharmacology
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type III / metabolism
  • Pregnancy
  • Promoter Regions, Genetic / drug effects
  • Sp1 Transcription Factor / biosynthesis
  • Umbilical Veins / cytology
  • Vasoconstrictor Agents / pharmacology
  • Vasodilation / drug effects
  • Vasodilation / physiology*


  • Cationic Amino Acid Transporter 1
  • Enzyme Inhibitors
  • Insulin
  • SLC7A1 protein, human
  • Sp1 Transcription Factor
  • Vasoconstrictor Agents
  • Nitric Oxide
  • 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
  • Arginine
  • Nitric Oxide Synthase Type III
  • Lysine
  • Ethylmaleimide