[Alcohol, tobacco and cannabis: Review of teratogenicity studies in animals]. / Alcool, tabac et cannabis: revue des études de tératogenèse chez l'animal.

Despite an intensive national campaign of information, the drugs most frequently consumed by young adults undoubtedly continue to be alcohol, tobacco and cannabis. If the impact of these drugs on the health of the consumers can be evaluated in conjunction with the clinical and epidemiologic data, the consequences on the embryo due to their consumption by the pregnant women can be appreciated thanks to the abundant literature describing their effects in the gravid animal. Taking into account the abundant literature available in multiple animal species, the zero drug recommendation should be widely diffused to pregnant women.

[Toxicology of reproduction: predictive value of experimental models. Round Table No 1 at Giens XIII]. / Toxicologie de la reproduction: valeurs prédictives des modèles expérimentaux. Table Ronde No 1 de Giens XIII.

The carrying out of clinical trials with a view to the marketing of drugs for human use is directly related to results of some animal studies. This workshop was devoted to evaluation of the quality and interest of these experimental models in reproductive toxicology. The predictive ability of preclinical trials to make extrapolations from animals to man decreases from foetotoxic to tetratogenic risks respectively and from the effects on fertility in both sexes to postnatal risks. As a result of this workshop, we propose the following improvements: (1) standardization and generalization of fertility test evaluations, especially the spermogram, in order to improve animal and human correlations; (2) development of knowledge and standardization of the follow up of the oestral cycle; (3) improvement of standardization, harmonization and diffusion of postnatal tests that prove relevant in animals; (4) increase in initiatives aimed at better mutual understanding of all drug partners; (5) creation of registers for new drugs, as soon as possible during clinical trials, to study their effects on the whole reproductive process; (6) recommendations for the creation of guidelines for International Conference on Harmonisation (ICH) to enable classification of observed effects in experimental models. This could lead to specific (potentially for each phase of the reproductive cycle) guidelines, precautions for use and/or contraindications which are listed in the summary of product characteristics.

Cell proliferation, migration and CAM-dependent neurite outgrowth as developmental in vitro endpoints for screening teratogenic potential: Application to valproic acid and related analogues of varying potency.

The in vivo teratogenic potential of valproic acid (VPA) and related teratogenic and non-teratogenic analogues has been correlated with their effects on specific in vitro endpoints of cell proliferation, migration and CAM-dependent neurite outgrowth, as these events are common to crucial epochs of development. The (+/-)-2-n-propyl-4-pentynoic acid [(+/-)-4-yn-VPA] and S-2-n-propyl-4-pentynoic acid [S(-)-4-yn-VPA] analogues increased the incidence of neural tube defects in mouse embryos exposed to a single dose, whereas the E-2-n-propyl-2-pentenoic acid (E-2-en-VPA) analogue and R-2-n-propyl-4-pentynoic acid [R( + )-4-yn-VPA] enantiomer were without effect. VPA and related analogues tested exerted comparable G1 phase antiproliferative effects in C6 glioma and limb bud cells in a dose range of 0-3 mM; however, their relative potency did not correlate with in vivo teratogenicity. In contrast, VPA and all teratogenic analogues, at 3 mM, inhibited neuronal cell aggregation and limb bud chondrocyte differentiation in a manner that exhibited a reasonable correlation with their in vivo teratogenicity. The teratogenic S(-)-4-yn-VPA and non-teratogenic R( + )-4-yn-VPA enantiomers exhibited a differential inhibition of primary neurone outgrowth of neuntes stimulated by cell adhesion molecules [L1 and N-cadherin (NCAD)]. Half-maximal inhibition was observed at approximately 150 muM for the teratogenic S(-)-4-yn-VPA enantiomer, but not the non-teratogenic R( + )-4-yn-VPA form. These results suggest that in vitro perturbations of differentiation are likely to provide the greatest discriminatory power for in vivo teratogenicity.

A whole-embryo culture system proposed to study mouse sexual determination.

Standard procedures to culture rodent embryos (2-4 somite explanted embryos and a 48-hr culture period), do not allow assessment of genital crest differentiation. Cultures of older embryos have to be used for this objective. The proposed method uses glass apparatus derived from those initially decribed by New (1967) and Cockroft (1973). Each apparatus allows the culture of six embryos in 80ml of a permanently gassed (95% O(2)) and circulating culture medium [Waymouth's medium-Hanks' balanced salt solution-rat serum (40:40:20, by vol.)]. In this system, 24 embryos (four groups of six) can be cultured under the same experimental conditions. In the mouse, the genital crest begins to develop on gestation day (GD) 9 and differentiation can be observed between GD12 and GD13 [GD0 = middle of the mating period (09.00-11.00 hr)]. GD12 mouse embryos were cultured for 30 hr. An in vitro /itin vivo comparison of survival rate, development and morphology was performed. Serial sections of cultured embryos were taken for microscopic examination. Survival rate proved to be 82% using this method. No delay in general development was observed. Histological examination demonstrated that gonadal determination in cultured embryos also paralleled differentiation in vivo. The results clearly demonstrate that a 30-hr culture period of GD12 mouse embryos enables the study of the murine sexual determination.

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.

Specific teratogenic action of 2,4,5-trichlorophenoxyacetic acid on mouse and rat whole-embryo cultures.

The effects of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were studied at concentrations ranging from 0.17 to 3.52 mm on post-implanted mouse and rat embryos cultured for 48 hr, either in the absence of any metabolic activation system or in the presence of mouse and rat S-9 mix. 2,4,5-T proved to be a potential teratogen, at 0.88 and 1.76 mm, on mouse embryos in the absence of any metabolic activation system. In the presence of mouse S-9 mix, 2,4,5-T showed a high teratogenic potential at 0.17, 0.88 and 1.76 mm. In contrast, in the presence of rat S-9 mix, 2,4,5-T induced structural defects only at 1.76 mm. At 3.52 mm, 2,4,5-T was 100% embryolethal with or without S-9 mix. On rat embryos, 2,4,5-T was potentially teratogenic only in the presence of mouse S-9 mix, causing a significant increase in dysmorphogenic effects at 0.17, 0.88 and 1.76 mm. With or without rat S-9 mix, 2,4,5,-T was only embryolethal to rat embryos at 1.76 and 3.52 mm. The abnormalities mainly involved the forebrain, the midbrain and the branchial arches. These results are consistent with the known in vivo embryotoxic action of this compound.