Analysis of limb anomalies induced in vitro by vitamin A (retinol) in mice.

Forelimb buds of day 11 ICR-JCL mouse embryos were cultured on liquid medium consisting of 90% Eagle's MEM and 10% fetal calf serum. Experimental medium contained 10 iu/ml vitamin A alcohol (retinol). In controls four of five metacarpals chondrified and the epidermis began to keratinize after 3-4 days of culturing. In experimental explants many pycnotic cells were observed in the peripheral mesenchyme in the hand plate, especially in pre- and postaxial regions. Only 2-3 metacarpals chondrified, and keratinization was inhibited in the experimental explants. Uptake of labeled sulfate was suppresssed by vitamin A. Excess vitamin A is thus thought (1) to act directly on limb buds, and thereby to induce limb anomalies, (2) to induce cell death in the mesenchyme, (3) to suppres the formation of chondroitin sulfate, and (4) to inhibit keratinization.