Effect of vitamin C on the availability of tetrahydrobiopterin in human endothelial cells

J Cardiovasc Pharmacol. 2001 Mar;37(3):333-8. doi: 10.1097/00005344-200103000-00012.


Vitamin C has long been known for its beneficial vascular effects, but its mechanism of action remains unclear. Recent reports suggest that vitamin C may prevent endothelial dysfunction by scavenging free radicals and increasing the bioavailability of nitric oxide. To investigate this area further, we studied the effect of vitamin C (10(-4) M) and Mn(III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP; 10(-5) M), a scavenger of superoxide, hydrogen peroxide, and peroxynitrite, on endothelial nitric oxide synthase (eNOS) enzymatic activity in cultured human umbilical vein endothelial cells. L-Citrulline formation (a measure of eNOS enzymatic activity) was significantly increased in cells treated for 24 h with vitamin C. No effect was observed after MnTBAP treatment. Chronic administration of vitamin C also had no effect on eNOS protein expression. Treatment with vitamin C for 24 h significantly increased levels of the eNOS co-factor tetrahydrobiopterin (BH4), whereas MnTBAP did not affect its levels. Sepiapterin (10(-4) M), a precursor of BH4, significantly increased eNOS activity, whereas addition of vitamin C to cells treated with sepiapterin did not cause any further increase in eNOS activity. Our results suggest that the beneficial effect of vitamin C on endothelial function is best explained by increased intracellular BH4 content and subsequent enhancement of eNOS activity. This effect appears to be independent of the ability of vitamin C to scavenge superoxide anions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Ascorbic Acid / pharmacology*
  • Biopterin / analogs & derivatives*
  • Biopterin / metabolism*
  • Cells, Cultured
  • Endothelium, Vascular / metabolism*
  • GTP Cyclohydrolase / metabolism
  • Humans
  • Immunoblotting
  • Metalloporphyrins / pharmacology
  • Nitric Oxide Synthase / metabolism
  • Nitric Oxide Synthase Type III


  • Metalloporphyrins
  • manganese(III)-tetrakis(4-benzoic acid)porphyrin
  • Biopterin
  • NOS3 protein, human
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type III
  • GTP Cyclohydrolase
  • sapropterin
  • Ascorbic Acid