PREVENTION BY HYDROXYUREA OF VEGETALIZATION OF SEA URCHIN LARVAE INDUCED BY cAMP PHOSPHODIESTERASE INHIBITORS.

During 3-hr treatment of the morulae of sea urchin with cAMP phosphodiesterase (PDE) inhibitors, which produce vegetalized larvae, incorporation of H-thymidine into DNA occurs at almost the same rate as in control embryos. DNase I digests the newly synthesized DNA in chromatin isolated from morulae treated with PDE-inhibitor (caffeine) faster than that isoloated from normal morulae whereas it dogests DNA isolated from chromatin in caffeine treated embryos at almost the same rate as that in normal embryos. Hydroxyurea, an inhibitor of nucleside diphosphate reductase, prevents the vegetalizing effect of PDE-inhibitor on the development of sea urchin embrys.