The effect of prostaglandin I on the contractility of the term pregnant human myometrium.
Small myometrial strips were dissected from the upper and lower segments of the term pregnant human uterus. The specimens were superfused in organ chambers and contractile activity was recorded isometrically. In strips from the upper segment, prostacyclin (PGI2), induced an initial excitatory response followed in the majority of experiments by transient inhibition. In the lower segment the response was generally the same although direct inhibition without initial stimulation occurred in some cases. During the period of inhibition the specimens were refractory to iterated exposure to PGI2. Furthermore, during this period of PGI2-induced inhibition the muscle strip was also refractory to PGE2 but responded to PGF2 alpha and oxytocin by stimulation. After inhibition of spontaneous contractile activity induced by indomethacin PGI2 induced an excitatory response. The results do not indicate any critical change in the myometrial responsiveness of the upper uterine segment to PGI2 during labor. In strips from the lower segment obtained before labor there tended to be a dominance of non-responders and inhibition only as compared to the results during labor. Nevertheless, whether or not PGI2 under physiological or pharmacological conditions has any significant influence on the contractility of the term pregnant human uterus, still remains obscure. As judged from earlier reports from our laboratory and the present study it is evident that the uterine vessels are considerably more sensitive to the action of PGI2 than the myometrium.
D015237:Dinoprost; D015232:Dinoprostone; D004347:Drug Interactions; D011464:Epoprostenol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D009215:Myometrium / Q000502:physiology; D010121:Oxytocin / Q000494:pharmacology; D011247:Pregnancy; D011458:Prostaglandins E / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects*
D011458:Prostaglandins E; D011460:Prostaglandins F; D010121:Oxytocin; D015237:Dinoprost; D011464:Epoprostenol; D015232:Dinoprostone