Effect of cAMP on cytosol protein phosphorylation in placental tissue of different gestational age.

Phosphorylation of cytosol proteins in placental tissue of different gestational age has been studied. Cytosol protein phosphorylation was stimulated by exogenous cAMP only in term placentae and remained unchanged in first and second trimester placentae. Exogenous proteins, histone and casein, were intensively phosphorylated by cytosol kinases with maximal activities in first trimester cytosol preparations. Exogenous cAMP stimulated histone phosphorylation, but it had no effect on casein phosphorylation. On the basis of the obtained results it can be concluded that endogenous protein phosphorylation in first and second trimester placental cytosol is cAMP independent.