Interrelationships of glutathione reductase, 5-aminolevulinic acid dehydratase, and free sulfhydryl groups in the erythrocytes of normal and lead-exposed persons.

Blood lead, erythrocyte glutathione reductase (GSSG-R), 5-aminolevulinic acid dehydratase (ALA-D), and free sulfhydryl (SH) groups were measured in normal subjects and in those with occupational exposure to lead. With increasing blood lead concentration the activity of GSSG-R rises and that of ALA-D decreases. There is also a fall in the level of free SH with rising blood lead concentrations. There is a high degree of correlation between these parameters, and it is suggested that the changes represent part of a biological control mechanism to compensate for the reduction of available sulfhydryl groups by lead ions.