The Role of Cysteine in the Regulation of Blood Glutathione–Protein Mixed Disulfides in Rats Treated with Diamide

• Published in: Toxicology and applied pharmacology 1998-01, Vol.148 (1), p.56-64
• Main Authors: Di Simplicio, Paolo, Giannerini, Fabiola, Giustarini, Daniela, Lusini, Lorenzo, Rossi, Ranieri
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Chemical and industrial products toxicology. Toxic occupational diseases; Chromatography, High Pressure Liquid; Cysteine - physiology; Diamide - pharmacology; Disulfides - blood; Erythrocytes - drug effects; Erythrocytes - metabolism; Glutathione - blood; Glutathione Disulfide - blood; In Vitro Techniques; Injections, Intraperitoneal; Kinetics; Liver - drug effects; Liver - metabolism; Male; Medical sciences; Rats; Rats, Wistar; Sulfhydryl Reagents - pharmacology; Toxicology; Various organic compounds
• ISSN: 0041-008X; 1096-0333
• DOI: 10.1006/taap.1997.8305

The kinetics of GSH, GSSG, and thiol-protein mixed disulfides (RS-SP) of GSH (GS-SP) and cysteine (CYS-SP) were studied in rat blood and liver in the time range 0–120 min after treatment with 100 and 200 mg/kg ip of diamide. Total consumption (10 min) and regeneration (120 min) of blood GSH, matched by parallel increases and decreases in RS-SP, were observed. GSSG did not change appreciably. No dose–effect relationship was obtained with either treatment. On the contrary,in vitrotreatment of blood with 0.75 mmdiamide provoked the same trends of GSH and RS-SP asin vivo(e.g., reversible modifications), whereas treatment with 1.5 mmcaused drops and rises in GSH and RS-SP, respectively, without any subsequent return to control values. The presence of a hematic factor responsible for RS-SP regulation is hypothesized in thein vivoexperiment. Successive experiments involvingin vitropretreatment with 2 mmdiamide and treatment with 0.5 mmof various thiols indicated that cysteine (CYS), but not GSH orN-acetylcysteine, rapidly restored erthyrocyte GSH and RS-SP to their basal levels. No evident sign of hemolysis was observed in these experiments. These results indicate that CYS is a diffusible thiol important for RS-SP regulation. Analysis of whole blood of rats treated with 100 mg/kg ip diamide and the presence of two reversible peaks (about 10 times the corresponding control level) of CYS-SP and free CYS confirmed the plausible role of CYS in maintaining the reversibility of the process. Preliminary results in liver of rats treated with 100 mg/kg diamide indicated that CYS may act by metabolic cooperation between organs. We suggest that CYS may have a role in the regulation of the intracellular redox state of rat erythrocytes during oxidative stress.