Sertraline (SER), a tricyclic antidepressant, is considered to belong to the group of selective amine reuptake inhibitors. Its ability to cross the blood-brain barrier and transplacental transport has been reported previously. It is widely distributed in the brain and is bound to human glutathione S-transferase-pi (GST-pi). If SER is taken during pregnancy, it gets accumulated in the embryo and fetus, and some studies have suggested it may cause congenital malformations, thus the study of the interaction of GST-pi with antidepressants is crucial. In this study, the interaction of human placental GST-pi with SER in the presence of the natural ligand, reduced glutathione (GSH) and a xenobiotic ligand, 1-chloro-2,4-dinitrobenzene (CDNB) was investigated. The V-m values obtained at variable [CDNB] and variable [GSH] were 61.3 +/- 2.3 and 46.4 +/- 1.7 U/nng protein, respectively. The k(cat) and k(cat)/K-m values for GSH and CDNB were 3.63 x 10(6) s(-1), 2.59 x 10(10) M-1 s(-1) and 4.79 x 10(6) s(-1), 1.29 x 10(10) M-1 s(-1), respectively. The half maximal inhibitory concentration value for SER was 4.60 mM. At constant [CDNB] and variable [GSH] the inhibition type was linear mixed-type, with K-s, alpha, and K-i values of 0.14 +/- 0.02, 2.90 +/- 1.64, and 2.18 +/- 0.80 mM, respectively. On the other hand, at fixed [GSH] and at variable [CDNB], the inhibition type was competitive, with K-i value of 0.96 +/- 0.10 mM. Thus, these findings weaken the importance of the protective role of GST against toxic electrophiles in vivo in adults, but due to its immature enterohepatic system SER may accumulate in the fetus and cause congenital malformations.