Cyclic AMP and Contractility of the Human Oviduct

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Abstract
Small strips from the circular and longitudinal smooth muscle layers at the ampullary-isthmic junction of the human oviduct were used for recording of contractile activity in organ baths and for determination of tissue levels of c[cyclic]AMP after exposure to prostaglandins [PG] and adrenoceptor agonists. PGF2.alpha. decreased cAMP Levels significantly at 2.5 min in both muscle layers, concomitant with its maximal stimulatory effect on contractile activity. PGE2 increased tissue levels of cAMP In circular strips, accompanied by inhibition of the spontaneous contractile activity. Exogenous dibutyryl cAMP as well as IBMX [isobutylmethylxanthine], an inhibitor of the phosphodiesterase activity, caused inhibition of myogenic activity in both preparations, an effect which could not be overcome by PGF2.alpha.. In longitudinal muscle specimens, the mechanical stimulation produced by PGE2 was not accompanied by a significant alteration in cAMP concentration. .alpha.-Adrenoceptor stimulation, giving an excitatory mechanical response in both layers, did not affect cAMP levels. Neither was mechanical inhibition caused by .beta.-adrenoceptor agonists accompanied by alteration of tissue cAMP content. Alteration of intracellular cAMP levels is one of the mechanisms which could regulate myogenic activity in the human oviduct, and tissue cAMP content may be influenced both by PGE2 and PGF2.alpha.. Altered tissue cAMP levels are not prerequisites for the contractile effects evoked by adrenoceptor agonists.