Methionine and Cysteine Affect Glutathione Level, Glutathione-Related Enzyme Activities and the Expression of Glutathione S-Transferase Isozymes in Rat Hepatocytes , ,

Abstract

Methionine and cysteine are constituents of glutathione. To understand the effects of these two sulfur amino acids on the glutathione (GSH)-dependent detoxification defense system, intracellular GSH and GSH-related enzyme activities, including GSH peroxidase, GSH reductase, GSH S-transferase (GST) and gamma-glutamylcysteine synthetase, were determined. In addition, the expression of three GST isozymes and carbonic anhydrase III (CA III) was examined. Hepatocytes isolated from male Sprague-Dawley rats were cultured with 0.1, 0.3, 0.5 or 1.0 mmol/L each of L-methionine and L-cysteine, for up to 7 d. Cells incubated with 0.5 or 1.0 mmol/L methionine and cysteine had increased intracellular GSH. A twofold increase was observed on d 6 compared with freshly isolated hepatocytes (P < 0.05). However, intracellular GSH was lower in cells treated with 0.3 or 0.1 mmol/L each of methionine and cysteine than in cells tested with 0.5 or 1.0 mmol/L. Although the GSH level differed significantly between cells cultured with 0.3 or 1.0 mmol/L of methionine and cysteine, GSH-related enzymes did not differ at these two concentrations. The activity generally remained constant for the first 24 h, then increased up to d 4. Immunodetection analysis revealed no difference in the level of CA III and GST isoforms, Ya, Yb and Yp, with amino acids each at a concentration of at least 0.3 mmol/L. Yp expression steadily increased up to d 7. Most proteins decreased rapidly after 48 h when cultured with 0.1 mmol/L of methionine and cysteine; however, the Yp level increased up to d 6. In conclusion, results indicate that a twofold increase of intracellular GSH is reached by adding methionine and cysteine at a concentration >0.5 mmol/L to the culture medium. The concentrations of methionine and cysteine for maintaining hepatic GSH are higher than for GSH-related enzyme activity and for GST isoform expression.

The Mitogen-Activated Protein Kinase Kinase (Mek) Inhibitor Pd98059 Elevates Primary Cultured Rat Hepatocyte Glutathione Levels Independent of Inhibiting Mek

“…The Chee's medium used in this study contains 62.6 mg/l L-cystine⅐2HCl (ϳ0.2 mM) and 60 mg/l L-methionine (ϳ0.4 mM) but does not contain any cysteine. It has been reported that GSH levels in hepatocytes are increased by the addition of cysteine or methionine in a concentration-dependent manner up to 2 mM (Wang et al, 1997). These results, in conjunction with the results of the present study, suggest that the elevation of cellular cysteine levels induced by PD98059 and flavone may be responsible for the increased GSH synthesis in primary cultures of rat hepatocytes.…”

l-Methionine Toxicity in Freshly Isolated Mouse Hepatocytes Is Gender-Dependent and Mediated in Part by Transamination

“…Dever and Elfarra at ASPET Journals on May 11, 2018 jpet.aspetjournals.org teine formation from the Met TM pathway (Wang et al, 1997). Met has also been shown to inhibit cellular GSH efflux by 50 to 70% in Met-exposed rat hepatocytes, possibly by allosteric inhibition of the GSH transport system, resulting in higher cellular GSH levels compared with control cells (Aw et al, 1986).…”

The effects of an L-methionine combination supplement on symptoms of upper respiratory tract infections and performance in ultramarathon runners before, during and after ultra-endurance exercise

“…32 The 5 active substances (L-methionine, vitamin B 6 , vitamin B 12 , folic acid and magnesium) in the supplement participate in the maintenance of glutathione status and have been shown to elevate intracellular glutathione. 16,31,33 Magnesium is an essential co-factor for the enzyme methionine adenosyl transferase, which forms S-adenosylmethionine (SAM) from L-methionine. 16 SAM can provide a methyl group to a variety of substances and S-adenosylhomocysteine (SAH) is formed as a product.…”