Differential alteration by thalidomide of the glutathione content of rat vs. rabbit conceptuses in vitro Jason M. Hansen a , Edward W. Carney b , Craig Harris a, * a University of Michigan, Department of Environmental and Industrial Health Toxicology Program, SPIM6116, 1420 Washington Heights, Ann Arbor, MI, 48109-2029USA b Developmental and Reproductive Toxicology, Health and Environmental Research Laboratory, The Dow Chemical Company, Midland, MI, USA Received 12 May 1999; received in revised form 16 July 1999; accepted 15 August 1999 Abstract Thalidomide has been shown to cause limb reduction defects in rabbits with much greater potency than in rats, possibly due to inherent biochemical differences between the two species. Whole embryo culture was used to make direct comparisons between thalidomide- sensitive New Zealand White rabbits and thalidomide-resistant Sprague-Dawley rats, focusing on the possible roles of glutathione (GSH) and cysteine in mechanisms of thalidomide teratogenicity. Conceptuses were treated by adding thalidomide (0, 5, 15, and 30 M) directly to the culture media containing conceptuses of similar gestational stages. Embryos and visceral yolk sacs (VYS) were measured for changes in GSH and cysteine content using HPLC after 24 h of exposure in vitro. Thalidomide-induced (15 and 30 M) depletion of VYS GSH occurred only in the rabbit, where GSH concentrations (pmol/g protein) fell significantly to about 50% of control. Rat VYS did not show a significant GSH depletion at any thalidomide concentration tested. Comparison between species showed that the control rabbit VYS contained 35% less GSH than the control rat VYS. Control rat embryos and control rabbit embryos contained similar concentrations of GSH, but thalidomide treatment preferentially depleted GSH in the rabbit at lower thalidomide concentrations (5 M). Cysteine concentrations were not significantly altered from control in the embryo or VYS of either species when treated with thalidomide. However, although control cysteine concentrations did not differ significantly between rat and rabbit VYS, control cysteine levels in rabbit embryos were 65% lower than those in control rat embryos. Rabbit conceptuses displayed lower species-specific GSH and cysteine levels and a greater propensity for thalidomide-induced GSH depletion than in rat conceptuses, consistent with the greater sensitivity of the rabbit to thalidomide teratogenicity. These thalidomide-induced and inherent species differences implicate a possible role for GSH and redox status in the mechanisms of thalidomide teratogenicity. © 1999 Elsevier Science Inc. All rights reserved. Keywords: Thalidomide; Glutathione; Redox status; Developmental toxicology; Teratology; Whole embryo culture; Oxidative stress. 1. Introduction Thalidomide (-phthalimidophthalimide) was intro- duced as a mild sedative-hypnotic in the late 1950s and was shown to cause various birth defects affecting the limb, ocular, respiratory, gastrointestinal, urogenital, cardiovascu- lar, and nervous systems [1]. Limb defects, manifested as phocomelia, amelia, micromelia, oligodactyly, and syndac- tyly, were the most easily detectable and the most common malformations. An estimated 5850 (and possibly more un- reported) newborns manifested thalidomide-induced pho- comelia worldwide, with many individuals not surviving past 3 years of age [1,2]. In the past 10 years, thalidomide has been shown to have therapeutic potential for treating leprosy and other diseases, including certain symptoms as- sociated with acquired immune deficiency syndrome in HIV-infected individuals [3,4]. It is clear that thalidomide can be beneficial against specific diseases, and for that reason, the Food and Drug Administration has approved it for medicinal use in the United States starting in 1999 [3]. Despite new information regarding its therapeutic applica- tions, the mechanisms by which thalidomide produces birth defects are still not well understood. Several hypotheses have been advanced to explain how thalidomide causes limb reduction defects. Mechanisms in- volving DNA intercalation, acetylation of macromolecules, * Corresponding author. Tel.:734 –936-3397; fax: 734-647-9770. E-mail address: charris @umich.edu Reproductive Toxicology 13 (1999) 547–554 0890-6238/99/$ – see front matter © 1999 Elsevier Science Inc. All rights reserved. PII: S0890-6238(99)00053-2