Exogeneous cyclic AMP blocks the muscarinic receptor-mediated intracellular Ca2+-release in the gastrulating chick embryo cells.

Exogeneous cyclic AMP (cAMP, 10-8M), when added together with acetylcholine (ACh, 500 µM) to dissociated chick embryo cells, blocked the ACh-stimulated increase in the level of cytosolic free Ca2+ ([Ca2+]i). This inhibiting action of exogeneous cAMP is probably mediated by intracellular cyclic GMP (cGMP) and cAMP.

Ultrastructural localization of adenylate cyclase and cAMP phosphodiesterase in the gastrulating chick embryo.

The ultrastructural localization of adenylate cyclase (E.C. 4.6.1.1.) and cAMP phosphodiesterase (PDE) (E.C. 3.1.4.17.) in the ectoderm of the developmental stage 4 chick embryo was studied. Adenylate cyclase was localized in the lateral surfaces of the ectodermal cells. In the primitive streak cells the enzymatic activity was observed on all the lateral surfaces, whereas in the periphery of the blastoderm the reaction product was localized in the apical parts of the lateral plasma membranes only.cAMP PDE localized in the apical cytoplasm of the ectodermal cells, with highest activity in the globular projections.