Prostaglandin-induced luteolysis in pregnant and pseudopregnant rabbits and the resultant effects on the myometrial activity.
The effect of prostaglandin (PG)-induced luteolysis on the myometrial activity in 20--21-day-pregnant and 11--12-day-pseudopregnant rabbits was studied by intrauterine pressure (IUP) recording during PG infusions. The same dose of PG (10 micrograms/h during 8h) was also given to 7 non-pregnant (untreated) does that were used as controls. Peripheral plasma concentration of progesterone and oestradiol-17 beta were measured at 2-h intervals during the infusion. Plasma progesterone level decreased significantly within 2 h or the start of infusion in pregnant and pseudopregnant does and continued to decrease; at the end of 8 h, the concentrations were 31 and 41%, respectively, of the pre-infusion levels. The amplitude of uterine contractions increased significantly after 4 h in pseudopregnant does, increased slightly but insignificantly in the pregnant does and showed no significant change in the non-pregnant does during PG infusion. The amplitudes developed in the pregnant and pseudopregnant does were significantly different. The direct effect of progesterone (1--3 micrograms/h during 4 h) was also studied in 7 non-pregnant rabbits. After 2 h the amplitude of contractions had decreased markedly and the pattern of activity had become irregular. The results support the concept of a myometrial inhibitory factor other than progesterone in rabbit pregnancy and suggest that this factor(s) originates in conceptus.
D000818:Animals; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D005260:Female; D009215:Myometrium / Q000187:drug effects / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000097:blood / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology; D011555:Pseudopregnancy; D011817:Rabbits; D014590:Uterine Contraction / Q000187:drug effects
D011460:Prostaglandins F; D011374:Progesterone; D004958:Estradiol