Modulation of amnionic adenylate cyclase and cAMP phosphodiesterase by prostaglandins E1 and F2 alpha.

The action of prostaglandins E1 and F2 alpha on adenylate cyclase and cAMP phosphodiesterase was assayed in cell membrane fractions of amnion obtained before and after labor from term physiological pregnancies. Both prostaglandins stimulate the activity of adenylate cyclase in a dose-dependent manner. After spontaneous delivery both prostaglandins stimulate the activity of phosphodiesterase at lower doses and inhibit it at higher ones while the stimulatory effect of low doses is missing before labor.

Receptor-mediated supra-additive activation of guinea pig superior cervical ganglion adenylate cyclase: role of Mn2+ ions and calmodulin.

The effects of Mn2+ and calmodulin were studied on the basal and agonist-modulated adenylate cyclase activity of the guinea pig superior cervical ganglion. The divalent cation strongly stimulates the basal and agonist-modulated enzyme in a concentration-dependent manner. Moreover, in the presence of Mn2+ the inhibitory effects of "high" GTP concentrations and of D-Ala2-Met-enkephalinamide on adenylate cyclase are eliminated, while the stimulation exerted by prostaglandin E2 and the supra-additive activation of the enzyme by the combination of the two drugs are unaffected.

RMI 12330A, an inhibitor of adenylate cyclase and cyclic AMP-phosphodiesterase activities in the segmental ganglia of the leech Hirudo medicinalis.

The effect of RMI 12330A, an inhibitor of basal as well as serotonin-stimulated adenylate cyclase in the segmental ganglia of the leech Hirudo medicinalis, has been tested on cyclic AMP-phosphodiesterase activity in the same tissue. The drug dose-dependently inhibits high and low affinity enzyme, an effect first evident at an RMI 12330A concentration of 0.5 mM.

Adenylate cyclase and cyclic AMP-phosphodiesterase activities of fetal membranes: effect of insulin.

Basal activity and response to insulin of adenylate cyclase and cyclic AMP-phosphodiesterase were measured in the fetal membranes before and after labor. Basal activity of adenylate cyclase showed only slight variations after delivery when compared to that observed before labor. Enzyme activity was significantly although weakly decreased by insulin both in the amnion and in chorion before labor, while after delivery a weaker non-significant inhibition was observed.

Effects of serotonin, dopamine and prostaglandin E(2) on adenylate cyclase activity and cyclic AMP levels in different ganglia of the freshwater snail Planorbis corneus L.

The effects of different neuroactive agents on cyclic AMP level of selected ganglia of Planorbis corneus were studied. Serotonin, dopamine and prostaglandin E(2) were capable of increasing significantly cyclic AMP synthesis in all the preparations. When such substances were tested in pairs, supra-additive effects were always observed.

[Preliminary studies on the characterization of adenylate cyclase from segmental ganglia of the leech Hirudo medicinalis].

Adenylate cyclase activity has been measured in segmental ganglia of the leech Hirudo m. Basal enzymatic activity was stimulated in a dose dependent fashion by serotonin. GTP is required in order to evoke maximal stimulation.