[Changes of oxytocin, progesterone, estradiol and CAP around the labor by prostaglandin F2 alpha (author's transl)].

In order to elucidate the mechanism of prostaglandin F2 alpha (PGF2 alpha) action to onset of labor, the author observed the changes in maternal peripheral plasma oxytocin, progesterone, estradiol and cystine-aminopeptidase (CAP) activity around the onset of labor by PGF2 alpha. For the investigation, 66 normal pregnant women from 6 to 10 gestational months and same numbers from 39 to 41 gestational weeks were chosen. The blood samples for the latter were drawn just before drip infusion of PGF2 alpha, 5-minutes interval, 3-minutes interval of pain and just after labor. PGF2 alpha administered for labor induction intravenously, and 55 pregnant delivered. 1) The maternal peripheral mean plasma concentrations of them showed increase during pregnancy. There were positive correlations between oxytocin and progesterone, estradiol, CAP. 2) During labor, oxytocin levels increased significantly (p less than 0.01) and progesterone levels decreased significantly (p less than 0.01). On the other hand estradiol levels did not change significantly. CAP levels showed irregular changes. Estradiol-progesterone ratio showed gradual increase. 3) Then during labor, progesterone levels showed negative correlation with oxytocin levels. From this study, the results indicate that significant changes in oxytocin and progesterone and gradual increase estradiol-progesterone ratio are concerned in the onset of labor caused by PGF2 alpha, so labor may progress dynamically.