Effects of QA 208-199 and its metabolite 209-668 on embryonic development in vitro after microinjection into the exocoelomic space or into the amniotic cavity of cultured rat conceptuses.

The objective of this study was to determine the direct embryotoxic effects in vitro of N-hydroxy-N-methyl-7-propoxy-2-naphthalene-ethanamine (QA 208-199, QAB) and of one of its metabolites, 7-propoxy-naphthalene-2-ylacetic acid (209-668, QAA), after circumventing the bioconverting conceptual membranes. The compounds were, therefore, microinjected either into the exocoelomic space or into the amniotic cavity of rat conceptuses of 10 d at prenatal age at doses of up to 84.9 ng (QAA) and 180 ng (QAB) per conceptus respectively. The conceptuses were subsequently cultured for 28 h after which their development was assessed. QAB produced marginal effects on embryonic differentiation only after microinjection of the compound into the amniotic cavity. Dysmorphogenic effects, however, occurred in a dose-dependent fashion after either exocoelomic or intraamniotic microinjections of the compound. The frequencies and types of anomalies were similar after either exposure route and consisted predominantly of anomalies associated with axial rotation. QAA also impaired embryonic differentiation at only the high dose level of 84.9 ng per embryo and after intraamniotic injections only. Dysmorphogenic effects were observed in all experimental groups, although the differences were not statistically significant when compared with the concomitant controls. An increased proportion of anomalies observed were in the cephalic region as compared to the defects produced by QAB. These data suggest that QAA most probably is not the QAB metabolite responsible for the embryotoxic action of QAB in vitro. Furthermore, the results tend to confirm the suggested involvement of the visceral yolk sac membrane in mediating QAB embryotoxicity.