Evaluation of the teratogenic potential of chemicals in the rat.

On the basis of the results of a variety of teratogenicity studies in Sprague-Dawley-derived albino rats, carried out over several years in our laboratory, an appraisal of the principal experimental procedures is set forth. Various categories of chemicals were used for the evaluation of dosage-related teratogenic potency. Salicylate, prednisolone, cyclophosphamide, 5-hydroxytryptamine (serotonin), glycinonitrile, and dimethylformamide have proven to be teratogenic under certain of the experimental conditions used. Particular differences in the embryotropic effects of acetylsalicylic acid were caused by qualitative and quantitative changes of the vehicle. Fetal morphological abnormalities, classified either as 'malformations' or as 'anomalies', may occur independently of overt maternal toxicity and/or embryotoxicity. Further, they may be closely correlated with general inhibitory effects on growth. Drugs may affect developing tissues and organs selectively due to their pharmacological activity and/or specific organ toxicity. The limitation of maternal treatment to a very short period of gestation may disclose a specific susceptibility of developmental stages of the embryo or fetus. Finally, the importance of data collected from a historical control population to the interpretation of teratogenicity data is emphasised.