Combined L-citrulline and glutathione supplementation increases the concentration of markers indicative of nitric oxide synthesis

J Int Soc Sports Nutr. 2015 Jun 10;12:27. doi: 10.1186/s12970-015-0086-7. eCollection 2015.


Background: Nitric oxide (NO) is endogenously synthesized from L-arginine and L-citrulline. Due to its effects on nitric oxide synthase (NOS), reduced glutathione (GSH) may protect against the oxidative reduction of NO. The present study determined the effectiveness of L-citrulline and/or GSH on markers indicative of NO synthesis in in vivo conditions with rodents and humans and also in an in vitro condition.

Methods: In phase one, human umbilical vein endothelial cells (HUVECs) were treated with either 0.3 mM L-citrulline, 1 mM GSH (Setria®) or a combination of each at 0.3 mM. In phase two, Sprague-Dawley rats (8 weeks old) were randomly assigned to 3 groups and received either purified water, L-citrulline (500 mg/kg/day), or a combination of L-citrulline (500 mg/kg/day) and GSH (50 mg/kg/day) by oral gavage for 3 days. Blood samples were collected and plasma NOx (nitrite + nitrate) assessed. In phase three, resistance-trained males were randomly assigned to orally ingest either cellulose placebo (2.52 g/day), L-citrulline (2 g/day), GSH (1 g/day), or L-citrulline (2 g/day) + GSH (200 mg/day) for 7 days, and then perform a resistance exercise session involving 3 sets of 10-RM involving the elbow flexors. Venous blood was obtained and used to assess plasma cGMP, nitrite, and NOx.

Results: In phase one, nitrite levels in cells treated with L-citrulline and GSH were significantly greater than control (p < 0.05). In phase two, plasma NOx with L-citrulline + GSH was significantly greater than control and L-citrulline (p < 0.05). In phase three, plasma cGMP was increased, but not significantly (p > 0.05). However, nitrite and NOx for L-citrulline + GSH were significantly greater at 30 min post-exercise when compared to placebo (p < 0.05).

Conclusions: Combining L-citrulline with GSH augments increases in nitrite and NOx levels during in vitro and in vivo conditions.

Keywords: Glutathione; L-arginine; L-citrulline; Nitric oxide; Resistance exercise.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Arginine
  • Biomarkers / blood*
  • Body Mass Index
  • Citrulline / administration & dosage*
  • Citrulline / blood
  • Cyclic GMP / blood
  • Dietary Supplements
  • Double-Blind Method
  • Glutathione / administration & dosage*
  • Glutathione / blood
  • Healthy Volunteers
  • Human Umbilical Vein Endothelial Cells
  • Humans
  • Male
  • Nitrates / blood
  • Nitric Oxide / biosynthesis*
  • Nitric Oxide / blood
  • Nitric Oxide Synthase / metabolism
  • Nitrites / blood
  • Rats
  • Resistance Training
  • Young Adult


  • Biomarkers
  • Nitrates
  • Nitrites
  • Citrulline
  • Nitric Oxide
  • Arginine
  • Nitric Oxide Synthase
  • Glutathione
  • Cyclic GMP