Action of allopurinol and aspirin on rat whole-embryo cultures

The effects of allopurinol (HPP) at concentrations ranging from 0.33-1.83 mM and of aspirin (ASA) from 0.28-2.22 mM, were studied on the rat whole-embryo culture system. Embryos were explanted at day 10 of gestation and cultured for 48 h, either in the absence or in the presence of rat and human S9. HPP proved to be potentially embryolethal and teratogenic without any S9, while it was embryolethal with rat S9 and dysmorphogenic with human S9. ASA showed an embryolethal and teratogenic potency without any S9 samples. These responses were increased in the presence of rat S9, while ASA embryolethality was predominant with human S9. These results obtained on rat embryos in culture suggest a correlation between the species origin of the biotransforming system and the known teratogenicity of HPP in sensitive animal models. However, ASA elicited responses not in agreement with the known teratogenic response in rodents.