Glutathione conjugates of 2-bromohydroquinone (GSyl-BHQ) cause renal proximal tubular necrosis that is dependent upon the activity of gamma-glutamyl transferase (GGT). GGT is present in embryonic yolk sac and its activity increases with gestational age, suggesting that the developing embryo might be at risk from maternal exposure to glutathione conjugates or compounds which are shown to form glutathione conjugates. Studies in pregnant rats exposed on Day 9 of gestation to 400 or 800 micromol/kg BHQ or 20 micromol/kg 2-Br-(di-GSyl)HQ and examined on Day 11 of gestation suggested that the parent compound (BHQ) or a metabolite was nephrotoxic in the adult and dysmorphogenic in the embryo and that 2-Br-(di-GSyl)HQ was nephrotoxic but not dysmorphogenic at the dose tested (20 micromol/kg). Day 9 rat embryos were exposed to BHQ, 2-Br-6-(GSyl)HQ, or 2-Br-(di-GSyl)HQ in vitro for 48 hr to determine the relative dysmorphogenic activity of the parent compound and the two conjugates. In vitro exposure to BHQ (0-40 microM) resulted in dose-related decreases in somite number (SN), total protein, and developmental score (DEVSC), with no effect on yolk sac diameter (YSD), crown rump length (CR), head length (HL), or percentage abnormal embryos (%AE); 60 microM BHQ was embryolethal. Embryos exposed to 2-Br-6-(GSyl)HQ (0-120 microM) were not affected at concentrations below 120 microM, at which dose there were significant effects on protein, YSD, CR, HL, DEVSC, SN, and %AE. Embryos exposed to 2-Br-(di-GSyl)HQ had a significantly lower DEVSC at the 80 microM concentration and significantly lower YSD, protein, and DEVSC and significantly higher %AE at the 10, 25, and 120 microM concentrations. CR, HL, and SN were not affected at any exposure level with this compound. (Copyright (c) 1993 by Academic Press, Inc.)