Toxic. in Vitro Vol. 7, No. 4, pp. 335-339, 1993 0887-2333/93$6.00 + 0.00 Printed in Great Britain.All rights reserved Copyright © 1993PergamonPress Ltd EVALUATION OF THE TOXICITY OF DIFFERENT METAL COMPOUNDS IN THE DEVELOPING BRAIN USING AGGREGATING CELL CULTURES AS A MODEL F. MONNET-TscnuDI*, M.-G. ZURICHand P. HONEGGER Institute of Physiology, University of Lausanne, CH-1005, Lausanne, Switzerland AMtract--To evaluate their toxicity in the developing brain, eight metal compounds, [bismuth sodium tartrate (BiNA-tartrate), CdC12, COO2, HgC12, dimethyl mercury, NiCI2, TIC1 and triethyltin chloride (TET)] were tested in aggregating cell cultures of foetal rat telencephalon. The compounds were applied to the cultures continuously, either during an early developmentalstage (betweendays 5 and 14) or during and advanced stage of maturation (between days 24 and 34). Changes in the activities of cell type-specific enzymes were used as a criterion for toxicity. A general cytotoxic effect was observed after treatment with either CdC12, HgCI 2 or TET at 10-6M, and with T1CI at 10-SM. Selective effects were found with BiNa-tartrate and dimethylmercury. CoCI 2 did not modify the parameters tested, whereas a stimulant effect was found with NiC12.The effects of several compounds were development dependent: HgCI 2, TET and TICI were more toxic in immature cultures, whereas BiNa-tartrate, dimethylmercuryand NiC12were more effective in differentiated cultures. Introduction cell cultures have been extensively characterized and used as a model in studies of brain development Metal compounds belong to the environmental poilu- (Honegger, 1985 and 1987; Riederer et al., 1992; tants that are able to accumulate in various body Seeds, 1973; Seeds et al., 1977) as well as in neurotox- tissues. Their accumulation in the brain (Arvidson, icology (Honegger and Schilter, 1992 and 1993; 1990; Cook et al., 1984; Escourolle et al., 1977; White Honegger and Werffeli, 1988). et al., 1990) may affect higher cerebral functions (Lehotzky et al., 1990; O'Callaghan and Miller, 1988; Rheuhl and Chang, 1979; White et al., 1990). The Materials anti Methods severity of these effects may depend on the levels of Cell culture. Rotation-mediated aggregating cell metal ions to which the organism is exposed, as well cultures of foetal rat telencephaion were prepared as as on the duration of the exposure (White et al., described previously in detail (Honegger, 1985; 1990). Moreover, the vulnerability of the brain to Honegger and Matthieu, 1990; Honegger and neurotoxicants may change in the course of brain Schilter, 1992 and 1993). Briefly, the dissected and development (Cory-Slechta, 1990). The work de- pooled forebrains of 15-day-old rat foetuses scribed here was undertaken, therefore, to study the (Sprague-Dawley; Mad6rin AG, Fiillinsdorf, effects of various metal compounds in differentiating Switzerland) were dissociated mechanically by sub- brain cells, both at an early and at an advanced stage sequent passages through two nylon sieves (pore size of development. 200 g m and 115 # m, respectively). Each culture flask In this study, rotation-mediated aggregating cell (Delong) received 6 x 10 7 cells resuspended in serum- cultures of foetal rat telencephalon were used as a free chemically defined medium (modified Dulbecco's model. These three-dimensional cultures are able to Modified Eagle's Medium). They were maintained reproduce a series of morphogenic events occurring under constant gyratory agitation at 37°C, in an in vivo (such as cell proliferation and migration, atmosphere of 10% COJ90% humidified air. Media synaptogenesis, myelination) and thus to attain a were replenished by the exchange of 5 ml (of a total high degree of differentiation (Honegger, 1985; of 8 ml) of chemically defined medium per flask every Honegger and Matthieu, 1990). Aggregating brain third day (until day 14) and every second day there- after. At day 20, the cultures were divided between two separate flasks. *To whom correspondence and reprint requests should be addressed at: Institute of Physiology, University of Chemicals. The following metal compounds were Lausanne, 7 rue du Bugnon, CH-1005 Lausanne, used: bismuth sodium tartrate (BiNa-tartrate)(ICN Switzerland. Biochemicals, Plainview, New York, USA); cadmium Abbreviations: BiNa-tartrate = bismuth sodium tartrate; chloride (CdC12" 2H20 ) (Fluka); cobalt (II) chloride ChAT = choline acetyltransferase; CNP = 2',Y-cyclic (CoCl2) (Fluka); mercuric chloride (HgC12) (Fluka); nucleotide 3'-phosphohydrolase; GAD = glutamic acid decarboxylase; GS =glutamine synthetase; TET= dimethylmercury [(CH3)2Hg] (Aldrich); nickel (II) triethyltin chloride, chloride (NiCl2 . 6H20) (Fluka); thallium (I) chloride TIV 7/4---D 335