[Reduced glutathione and L-cysteine in endotoxic shock in the rat]

Reduced Glutathione (GSH) is a well known physiological antioxidant, that would protect against lethal effects of endotoxin. However, the site of the action of GSH can be intracellular (transmembrane passage of constitutive amino acids) or extracellular (membrane thiols).

To search if L-cysteine (one of three constitutive amino acids of GSH) protects against endotoxin as GSH and to search if inhibition of transmembrane passage of GSH and L-cysteine by Probenecid affects that protection.

Rats injected (n = 99) with a lethal dose of endotoxin (BACTO, DIFCO lab. 0111:B4 10 mg/kg ip) immediately after received: (a) Saline solution; (b) GSH 500 mg/kg; (c) L-Cysteine 0.25 g/kg; (d) Probenecid 25 mg/kg in 20% Ethanol plus GSH 500 mg/kg; (e) Probenecid 25 mg/kg in 20% Ethanol; (f) 20% Ethanol. The administration of Saline solution, GSH, L-cysteine was repeated two hours later. Injection volume was 0.5 ml ip. Survival rate of each group of rats was evaluated 6, 12 and 24 hours after endotoxin injection. Survival was compared with that of the control group by Fisher test.

GSH and L-cysteine significantly increase survival if compared to all other treatments (respectively p < 0.002 and p < 0.001 at 12 hours; p < 0.005 and p < 0.0002 at 24 hours). Probenecid nullifies the survival increase caused by GSH. Probenecid alone or Ethanol alone show a survival rate not significantly different in respect to control group.

Protection exerted by GSH against fatal effects of endotoxin is also provided by one of its constituent amino acids (L-cysteine) and is inhibited by Probenecid. So we can infer that such an antioxidant action happens at an intracellular site. Need of high doses of GSH and L-cysteine can be due to the necessity of a strong concentration gradient between extra and intracellular sites.