Effect of α- and β-Adrenergic Stimulation on the Uterine Motility and Adenosine 3′,5′-Monophosphate Level

Abstract

In experiments on isolated rat uteri the relation was studied between the mechanical effects of catecholamines and the level of adenosine 3′,5′-monophosphate (cAMP). Adrenaline (1–100 ng/ml) caused relaxation of isolated rat uteri and a highly significant increase in the tissue cAMP concentration; both relaxation and cAMP increase were blocked by propranolol or butoxamine but unaffected by phenoxybenzamine. The rise in cAMP level was maintained in a Ca-free solution when the muscle could not contract. The stimulation of α-receptors of propranolol-pretreated uteri induced contractions but it caused no change in the cAMP concentration. cAMP level, increased by a previous application of isoproterenol, remained unchanged when the uterus contracted after application of oxytocin, propranolol, or propranolol with adrenaline. cAMP levels remained elevated after previous adrenaline whether oxytocin dose–effect curves were still shifted to the right or were shifted back by subsequent propranolol. Adrenaline decreased significantly the ATP concentration in the uterus. The effect persisted with a propranolol blockade but was reversed to an increase by pretreatment with phenoxybenzamine or in a Ca-free solution. We conclude that the level of cAMP in the uterus is controlled by mechanisms related to β-receptors but that α-receptor mechanisms do not affect cAMP levels. Also the level of cAMP is not the primary determinant of uterine motility.

Effects of Phthalazinol, Eg 626, on Membrane and Mechanical Properties of Smooth Muscle Cells of Rabbit Main Pulmonary Artery and Superior Mesenteric Artery

“…activation of adenylate cyclase by (9-adrenergic agonist, resulting in inhibition of contractility (23)(24)(25). In fact, a good correlation could be demonstrated in a comparative study of the effects of noradrenaline on the uterine relaxation and adenylate cyclase activation, thereby providing evidence for regulatory role of cyclic AMP in uterine motility.…”

Effect of Rutin on the Isolated Rat Duodenum and Comparison with the Effects of Adrenaline, Isoprenaline and Papaverine

“…Catecholamines may cause relaxations of some smooth muscles (8)(9)(10)(11)(12)(13)(14), some vascular smooth muscles (8,(15)(16)(17), uterus (8,(18)(19)(20)(21)(22)(23). The action of catecholamines son these muscles is mainly due to beta-adrenoceptor activation and able to be blocked by beta-adrenergic blocking agents (12-14, 17, 19).…”

“…The action of catecholamines son these muscles is mainly due to beta-adrenoceptor activation and able to be blocked by beta-adrenergic blocking agents (12-14, 17, 19). Cyclic adenosine-3', 5'-monosphosphate (cyclic AMP) is believed to be the intracellular mediator of the effect of beta-adrenoceptor activation in the smooth muscles mentioned above (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). On the other hand, alpha-adrenoceptor activation may also cause relaxation of intestinal smooth muscle (9,(12)(13)(14).…”

Regulation by estrogen and progesterone of protein kinases in rabbit myometrium.

“…Uterine contractility is regulated in response to certain hormones such as oxytocin and epinephrine (16)(17)(18). A possible involvement of cAMP in the contractility has been demonstrated by the findings that stimulation of i3-adrenergic receptors relaxes the myometrium with a concomitant increase in cAMP (19,20). The stimulation of myometrial adenylate cyclase is inhibited by prostaglandins and oxytocin which are known to cause contraction.…”