Unexpected stimulatory effect of progesterone on human myometrial contractile activity in vitro.
OBJECTIVE
To investigate the effects of continuous exposure of progesterone on contractile activity of term human myometrium in vitro.


METHODS
Myometrial biopsy specimens were obtained from 14 term pregnant women undergoing elective cesarean. The specimens were immediately immersed in Hepes buffer and buffer containing 0.33, 4.1, and 70 micrograms/mL progesterone. Muscle biopsies were dissected along the bundles of smooth muscle under stereomicroscope. These myometrial strips were mounted in tissue baths and superfused with Hepes buffer and buffer containing different concentrations of progesterone.


RESULTS
The progesterone concentration of 0.33 microgram/mL had no significant effect on myometrial contractile activity. The concentrations of 4.1 and 70 micrograms/mL increased the frequency of contractions (P < .01 for each) and tonus (P < .01 for each), decreased the activity area of contractions (P < .01 for each), and delayed the onset of contractions (P < .01 and P < .05, respectively).


CONCLUSIONS
When the myometrium is not deprived of progesterone, this hormone may have excitatory effects on the frequency of contractions and tonus of the lower uterine segment of term human myometrium.
Department of Gynecology and Obstetrics, University Hospital, Uppsala, Sweden.
X
X
Fu
M
M
Rezapour
M
M
Löfgren
U
U
Ulmsten
T
T
Bäckström
D000328:Adult; D002585:Cesarean Section; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology* / Q000502:physiology; D014590:Uterine Contraction / Q000187:drug effects*
D011374:Progesterone