Free heme pool and activity of key enzyme of heme synthesis in the rat liver under action of agents affecting reduced glutathione level.

The decrease of GSH level in the rat liver was found to be accompanied by an increase of tryptophan 2,3-dioxygenase (TDO) heme saturation during first hours after HgCl2, phenylhydrazine (Ph) injection or rhabdomyolysis (the coefficient of correlation -0.978). The activity of the key enzyme of heme synthesis--5-aminolevulinate synthase (ALAS) was 2.5-fold increased in the first hours after Ph injection and rhabdomyolysis. Glutathione injection in vivo as well as CdCl2 caused the increase of GSH content and the inhibition of ALAS. The coefficient of correlation for GSH content and ALAS activity under the action of agents altering both these parameters (CdCl2, Ph, GSH injection and rhabdomyolysis) is 0.938. Taking into account the presence of heme regulatory motif with conserved cystein in many proteins, including ALAS and TDO (accession number in SwissProt database AAH61793 and P21643, respectively), the link between alterations of GSH content, ALAS activity and heme saturation of TDO in the rat liver could be proposed. The further experiments should be performed in order to elucidate the mechanisms of GSH level influence on free heme pool formation in the liver cells.