A diurnal variation of the glutathione content in rat liver and stomach

Recent studies have shown that it is possible to influence the synthesis and metabolism of GSH by administration of selective enzyme inhibitors or of certain precursors of this tripeptide. L-thiazolidin-4-carboxylic acid (TC) has the property of an intracellular cysteine delivery system and can be used to promote GSH synthesis. In animal and human studies it has been shown that TC possess a protective activity on SH groups. The aim of this research is to investigate the effect of TC on GSH content of rat liver and stomach. We observed a clear diurnal variation of GSH levels. This diurnal variation should be taken into consideration in any study of the effect of a treatment upon GSH levels. The changes in the concentrations of GSH in the liver and in the stomach when compared with the initial values can therefore be statistically significant and erroneously interpreted as due to the treatment if the time of day of the sampling is not taken into consideration. There are differences statistically significant between a.m. and p.m. values of the GSH; however the differences observed at each time between control and treated rats are not significant. The TC administration of 50 mg/kg did not increase the levels of GSH in liver and in stomach, but the levels of GSH were high and therefore amounts of this order of magnitude would be required in order to produce noticeable increases in GSH levels by administration of GSH precursor.