The significance of prostacyclin produced by pregnant rat myometrium: the relationship between myometrial prostacyclin producing activity and passive stretch of myometrium by growing conceptus.
The present experiment was performed to elucidate the significance of prostacyclin (PGI2) produced by pregnant rat myometrium. PGI2-like substance producing activity of various portions of the uterus was measured at selected gestational stages by platelet bioassay; surface area per 1 gm of uterine wall enveloping one conceptus was calculated; and spontaneous contractility of myometrium of both conceptus and non-conceptus regions and the effects of authentic PGI2 on it were examined. PGI2-like substance producing activity increased with advancing pregnancy, but the activity varied according to area of the myometrium, being highest in the area where it was most greatly stretched by the growing conceptus and lowest where no conceptus was contained. Spontaneous contractility was reduced in regions with high PGI2 producing activity. Though authentic PGI2 generally exhibited a stimulatory effect, it had an inhibitory effect on Day 10 pregnant myometrium. From these results, it may be concluded that the producing activity of PGI2, which remarkably increases in the conceptus region with the advance of pregnancy, keeps the uterine wall relaxed, making the uterus adapt to the growth of the fetus. Passive myometrial stretch by the growing conceptus is thought to be one of factors which enhance myometrial PGI2 producing activity.
Kawano
M
M
Department of Obstetrics and Gynecology, Miyazaki Medical College, Japan.
Mori
N
N
D000818:Animals; D004031:Diestrus / Q000502:physiology; D011464:Epoprostenol / Q000096:biosynthesis* / Q000494:pharmacology; D004971:Estrus / Q000502:physiology; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D007700:Kinetics; D009215:Myometrium / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D013499:Surface Properties; D013997:Time Factors; D014018:Tissue Distribution; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000033:anatomy & histology
D011464:Epoprostenol; D007213:Indomethacin