Developmental toxicity to TCDD-like congeners in fish, birds, and mammals, and reproductive toxicity in mammals are reviewed. In fish and bird species, the developmental lesions observed are species dependent, but any given species responds similarly to different TCDD-like congeners. Developmental toxicity in fish resembles "blue sac disease," whereas structural malformations can occur in at least one bird species. In mammals, developmental toxicity includes decreased growth, structural malformations, functional alterations, and prenatal mortality. At relatively low exposure levels, structural malformations are not common in mammalian species. In contrast, functional alterations are the most sensitive signs of developmental toxicity. These include effects on the male reproductive system and male reproductive behavior in rats, and neurobehavioral effects in monkeys. Human infants exposed during the Yusho and Yu-Cheng episodes, and monkeys and mice exposed perinatally to TCDD developed an ectodermal dysplasia syndrome that includes toxicity to the skin and teeth. Toxicity to the central nervous system in monkey and human infants is a potential part of the ectodermal dysplasia syndrome. Decreases in spermatogenesis and the ability to conceive and carry a pregnancy to term are the most sensitive signs of reproductive toxicity in male and female mammals, respectively.

A series of coumarins and delta3-isoflavenes was prepared. Although antifertility activity was shown by all of these compounds, the required dosage in mice varied from 13.5 mug/kg/day to 50 mg/kg/day. The most potent compounds were the 2-methyl-4-ethylisoflavenes, two of which (2a and 2b) were about equipotent with DES on a molar basis. They were followed by the 2,2-dimethylisoflavenes, the 2-unsubstituted isoflavene, and the coumarins. The most active compounds possessed an acetoxy group at C-7 and an oxygen function at C-4'. Presence of fluorine at C-4' or diethylaminoethoxy at C-M decreased the antifertility activity. The uterotropic activity followed the same trends as the antifertility activity with some evidence for the separation of the two effects in the 2,2-dimethylisoflavene series. Based on a limited study it appears that two phenolic hydroxyl groups are required for the presence of good estrogen receptor binding activity. An apparent lack of correlation between the estrogen binding activity and uterotropic or antifertility effects is probably explained by in vivo metabolism.

The development and validation of short-term tests that assess developmental toxicity have received increased attention due to the large number of agents that need to be tested and the desirability to reduce the overall use of animals in research and safety evaluation. The Short-Term In Vivo Reproductive Toxicity Test was developed to help meet this need and to provide a method for prioritizing agents for further testing. This report provides a brief overview of the risk assessment process and a focus on the aspects of test validation that should be considered when evaluating short-term tests. It is intended to give the reader an appreciation for many of the considerations that must go into developing and validating a short-term test, and to indicate areas within the risk assessment process where inclusion of such a test may be appropriate.

Aus dem Ketosäureester (I) erhält man nach bekannten Verfahren das Methylenketon (II), das über (IIIa) und (IIIb) in (IV) übergeführt wird.

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