Chemical-biological reactions common to teratogenesis and mutagenesis.

Cytotoxic chemicals have in common the ability to act specifically on cells in cycle. Bacteria are more sensitive in the exponential growth phase than when growing slowly in media. Similar observations have been made on a variety of systems ranging from bacteria, yeast, higher plants and invertebrates to vertebrates including primates. The embryo and fetus are highly susceptible to cytotoxic agents because they have continuous groups of cells in the growth phase. Acutely toxic doses may cause cellular death and result in developmental defects or fetal death. Cytotoxic agents can be grouped as alkylating agents, electrophilic reactants, antimetabolites, intercalating agents, amino acid antagonists, spindle poisons, and an additional group of chemicals which covalently bind to DNA. These cytotoxic groups of chemicals may also be mutagenic by interacting with DNA to produce changes in sequences of nucleotides resulting in heritable defects either in a somatic cell line or in a germinal cell line. The mechanisms of chemical-induced teratogenicity and mutagenicity are similar. This commonality is further discussed in the text.