The identification of a glutathione S-transferase isozyme in fetal rat livers which is absent from adult livers.

The subunit composition of adult and fetal rat liver glutathione S-transferase was investigated by affinity chromatography followed by polyacrylamide gel electrophoresis in sodium dodecylsulphate. Adult livers contained four major GSH S-T subunits. A previously unidentified subunit was detected in fetal livers. This subunit(s), which differed from that found in rat placenta, had a molecular weight of about 25,500 daltons, gave two bands of pI 8.0 and 8.5 on isoelectric focussing, and reacted on "Western blots" with antibodies raised against the major GSH S-T subunits of adult liver. Densitometric measurements suggest that the newly detected transferase subunit accounted for as much as 26% of GSH S-T in fetal livers.