Effects of bromo-cyclic GMP and bromo-cyclic AMP on embryonic development of Xenopus laevis

Low molecular signalling molecules such as cAMP and cGMP are expected to ha ve important functions in early morphogenetic processes in animal developme nt. We examined the effect of 8-bromocyclic GMP (Br-cGMP) on Xenopus embryo genesis, using 8-bromo-cyclic AMP (Br-cAMP) as a reference. When Xenopus ga strulae were cultured in the medium which contained these analogues, their development was affected in specific and dosage-dependent manners: While Br -cAMP induced anomaly only in head part (swelling of myelencephalon with en larged ventricle), Br-cGMP induced shortening in body length often accompan ied by bending of the cephalo-caudal axis. In embryos treated with Br-cGMP at a high dose, cellular movement was inhibited as revealed by SEM and this resulted in the formation of tadpoles with unclosed yolk plug. Br-cGMP at lower doses induced severe inhibition of the development of notochord and m uscles. Since HPLC analyses revealed that both analogues were uptaken into embryonic cells, we assumed that the morphological effects observed were in duced by the interference of the normal functioning of cGMP and cAMP, respe ctively, by Br-cGMP and Br-cAMP. Based on the results obtained, we assume t hat while cGMP is involved mainly in the differentiation of mesodermal stru ctures, especially in formation of notochord and muscles, cAMP is involved mainly in the differentiation of neural structures.