Effect of retinoic acid and valproate on sea urchin development.

: The effect of valproate and retinoic acid on Paracentrotus lividus development and fertilization is reported. Retinoic acid at concentrations between 5 microM and 7 microM causes severe disturbance of development and at 10 microM complete embryo degeneration if added in the period from fertilization on. Concentrations up to 7 microM are uneffective if retinoic acid addition is started 16 h after fertilization. Valproate at concentrations between 1 mM and 5 mM causes severe disturbances of development if added from 5 min after fertilization on. Concentrations of 20 mM are lethal to all embryos. If the drug is added 16 h after fertilization no effect is observed up to the concentration of 10 mM. The effect of valproate is specific, because its isomere 2-en at 10 mM has very little effect on development. Both drugs affect fertilization only at higher concentrations: more than 1 microM for retinoic acid and more than 10 mM for valproate.