title: Protective effect of black tea on integral membrane proteins in rat liver.
abstract: Ethanol intoxication is accompanied by oxidative stress formation. Consequently, it leads to disturbances in cellular metabolism that can alter the structure and function of cell membrane components. Black tea displays antioxidant properties, protects membrane phospholipids and may protect integral membrane proteins. In the present study, we examined whether black tea induces changes in the liver integral membrane proteins of 12-months old rats chronically intoxicated with ethanol. To estimate qualitatively and quantitatively the levels of the liver integral membrane proteins, the proteins were selectively hydrolyzed by trypsin, the obtained peptides were resolved by HPLC and the levels of specific amino acids within the individual peptides were determined. All of the obtained peptides contained phenylalanine (Phe), cysteine (Cys) and lysine (Lys). Compared to the control group, rats in the ethanol intoxication group showed decreased liver levels of integral membrane proteins as well as fewer trypsin-hydrolyzed peptides and amino acids in the hydrolyzed peptides. Administration of black tea to ethanol-intoxicated rats partially protected proteins against the structural changes caused by ethanol. Black tea prevented decreases in the levels of cysteine (in about 90% of cases), lysine (in about 60% of cases), phenylalanine (in about 70% of cases) and examined peptides (in about 60% of cases). The liver protein level was higher (by about 18%) in rats who received black tea and ethanol than in those who received ethanol alone. In conclusion, black tea partially protects the composition and level of rat liver cell integral membrane proteins against changes caused by ethanol intoxication.
authors.affiliation: Institute of Chemistry, University in Białystok, Al. Piłsudskiego 11/4, 15-443 Białystok, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Szachowicz-Petelska
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Skrzydlewska
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Figaszewski
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000975:Antioxidants / Q000302:isolation & purification / Q000494:pharmacology*; D028241:Camellia sinensis / Q000737:chemistry*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D056486:Chemical and Drug Induced Liver Injury / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D002851:Chromatography, High Pressure Liquid; D000431:Ethanol / Q000633:toxicity; D006868:Hydrolysis; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013662:Tea
chemical_list: D000596:Amino Acids; D000975:Antioxidants; D008565:Membrane Proteins; D013662:Tea; D000431:Ethanol