Recent evidence suggests that vitamin A exposure through over- the-counter supplements may be responsible for malformations in human infants. The vitamin A analogue, 13-cis retinoic acid (RA), is an established, potent human teratogen with ocular malformations observed following in utero exposure. Preliminary studies have demonstrated that exposure to 13-cis RA during gastrulation in mice results in a high incidence of anterior segment dysgenesis, particularly keratolenticular adhesions characteristic of Peters' anomaly. The first portion of this proposal is designed to characterize the embryogenesis of RA- induced ocular malformations. Sequential SEM, TEM, and LM analyses of the events leading to these malformations in exposed fetuses will provide further information about normal and abnormal anterior segment formation, particularly the relatively obscure process of lens detachment from the surface ectoderm. Immunocytochemistry will be used to evaluate the significance of fibronectin and laminin in this process. Previous animal studies of ethanol and 13-cis RA have demonstrated a remarkable similarity in their individual teratogenic effects when administered during the same developmental period. The second portion of this proposal is designed to investigate the combined effects of vitamin A and ethanol (agents to which humans are commonly exposed) at levels which, individually, are not teratogenic. Vitamin A is to be administered in one of two regimens: 1) chronically in the diet at levels to include those which are excessive but non-teratogenic, and 2) acute single dose by gavage on day 7, 0 hours of gestation (plug day = day 0). Pregnant females will be subsequently treated with ethanol intraperitoneally in two doses on day 7, 0 hours and day 7, 4 hours of gestation (during gastrulation). The timing is designed to result in peak serum levels of both agents simultaneously. HPLC will be used to quantitate the serum levels of vitamin A during gestation in all exposure groups. Studies of the developing fetuses will utilize SEM, TEM, light microscopy, and immunocytochemistry. Emphasis will be placed on quantitation of the incidence of eye malformations in each of the treatment combinations in order to determine if, in concert, these two agents are additive or interactive in their effects. Identification of an interactive effect may indicate similar mechanisms of action or effects on similar cell populations for these chemically dissimilar teratogens. Both vitamin A and ethanol are agents to which pregnant women could be intentionally exposed at doses which were previously believed harmless but which, in combination, may be teratogenic.
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| Stromland, K; Miller, M; Cook, C (1991) Ocular teratology. Surv Ophthalmol 35:429-46 |
| Cook, C S; Sulik, K K (1990) Laminin and fibronectin in retinoid-induced keratolenticular dysgenesis. Invest Ophthalmol Vis Sci 31:751-7 |
