title: Circadian variations in hepatic glutathione content, gamma-glutamylcysteine synthetase and gamma-glutamyl transferase activities in mice.
abstract: Experiments were conducted to determine if the circadian variations previously observed in hepatic reduced glutathione (GSH) concentrations also occurred in the associated enzymatic activities involved in the synthesis (gamma-glutamylcysteine synthetase) and degradation (gamma-glutamyl transferase) of glutathione using male CF-1 mice. All parameters were measured at four hour intervals over a 24-h period under normal (L: 0600-1800 h) and reversed (L: 1800-0600 h) lighting schedules. Circadian rhythms were found in each parameter under both lighting schedules. With GSH content, the rhythms' peak occurred at 0200 h and the nadir at 1400 h under the normal lighting schedule and was reversed (peak: 1800 h; nadir; 0600 h) under reversed lighting. The enzymatic activities also varied in a circadian manner with a phase shift in the peak and nadir occurring with a change in lighting schedule. Liver weight varied in a circadian manner under both lighting schedules with greatest weights occurring at the end of the dark phase. These data show that not only does GSH content vary in a circadian manner but that associated enzyme activities do as well. However, the hepatic enzyme activities did not correlate well with the GSH rhythm and, thus, do not provide a mechanistic rationale for the GSH rhythm.
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism*; D005978:Glutathione / Q000032:analysis*; D008099:Liver / Q000032:analysis* / Q000201:enzymology; D008297:Male; D051379:Mice; D009929:Organ Size; D010453:Peptide Synthases / Q000378:metabolism*; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
chemical_list: D005723:gamma-Glutamyltransferase; D010453:Peptide Synthases; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione