REPRODUCTION AND DEVELOPMENT

The currently developed and validated in vitro tests for female and ma le fertility and also for developmental toxicity are described and eva luated according to their potential use as screening or replacement al ternatives to the established in vivo tests in reproductive and develo pmental toxicology. Alternative methods today can only be used to eval uate a few specific components of the integrated reproductive function s in both females and males. However, in the field of developmental to xicity testing there is a strong theoretical and empirical basis for t he predictive power of in vitro screens using mammalian embryos as wel l as embryonic cells and tissues. Several of these assays have been va lidated or are currently undergoing validation in several laboratories and are >80% concordant with in vivo results. Failure to achieve 100% accuracy reflects the inherent limitations of these systems, which ar e manageable, as the concordance rates are still good. The level of co ncordance suggests that these assays are adequate for screening purpos es to complement traditional in vivo testing. The use of these assays as screens will save valuable in vivo testing resources for those comp ounds most likely to enter the market and to which people will be expo sed.