Alteration of Ca2+ homeostasis of sea urchin embryos by retinoid CD 367, dual effect on egg cleavage and embryonic development.

The effect of a light stable retinoid (CD 367) was studied on sea urchin embryos. CD 367 did not affect sperm-egg interaction. In a range of concentrations between 10 and 100 microM, CD 367 delayed the first and the second cleavages. When added after fertilization, micromolar amounts of CD 367 delayed hatching and produced embryonic abnormalities in a dose-dependent manner. Mesodermal cells, primary (PMC) and secondary (SMC) mesenchyme cells migration was particularly disturbed, leading to exogastrulations and calcified spicules malformations. Concentrations of CD 367 higher than 8 microM were embryolethal. Micromolar amount of CD 367 increased plasmalemma Ca2+ permeability of fertilized eggs but not of unfertilized eggs. CD 367 inhibited ATP-dependent intracellular sequestration of Ca2+ in a range of concentrations similar to those affecting egg cleavage and embryonic structures. Since we were unable to detect nuclear receptors for CD 367 in sea urchin eggs and ovocytes, these effects probably are not related to interaction of the retinoid with members of the RAR family, to which CD 367 has a high affinity, but rather to its toxicity by the means of some unknown mechanisms.