Prostaglandin production by the early pregnant guinea-pig uterus in relation to implantation and luteal maintenance, and the effect of oestradiol.

The outputs of prostaglandin (PG) F-2 alpha and PGE-2, but not of 6-oxo-PGF-1 alpha, from the guinea-pig uterus were significantly lower on Days 7 and 15 of pregnancy than on the corresponding days of the cycle. Uterine PGF-2 alpha output increased 28-fold between Days 7 and 15 of the cycle but only 4- to 5-fold between these same days of pregnancy. Uterine PGE-2 and 6-oxo-PGF-1 alpha outputs increased 2- to 3-fold between Days 7 and 15 of the cycle and of pregnancy. Endometrial PGF-2 alpha synthesizing capacity was 60-70% lower on Days 7 and 15 of pregnancy than on the corresponding days of the cycle, although it increased 2-fold and 2.5-fold between these days of pregnancy and of the cycle, respectively. Endometrial PGE-2 and 6-oxo-PGF-1 alpha synthesizing capacities showed no significant variation amongst Days 7 and 15 of the cycle and of pregnancy, except that endometrial PGE-2 synthesizing capacity was lower on Day 7 of the cycle. Oestradiol treatment (10 micrograms s.c. daily from Days 10 to 14 of pregnancy) did not affect plasma progesterone concentrations, uterine 6-oxo-PGF-1 alpha output, and endometrial PGF-2 alpha, PGE-2 and 6-oxo-PGF-1 alpha synthesizing capacities in 9/12 guinea-pigs when examined on Day 15. Uterine PGF-2 alpha and PGE-2 outputs increased 3- and 1.5-fold, respectively, in these guinea-pigs, but were still much lower than the outputs from the Day-15 non-pregnant uterus. The pregnancies appeared unaffected in these oestradiol-treated guinea-pigs. In the other 3 oestradiol-treated animals, uterine PGF-2 alpha output was 20- to 30-fold higher than in untreated, pregnant guinea-pigs on Day 15, and 2- to 3-fold higher than in Day-15 non-pregnant guinea-pigs. Uterine PGE-2 and 6-oxo-PGF-1 alpha outputs also tended to be higher in these treated guinea-pigs. In these 3 guinea-pigs, endometrial PGF-2 alpha, PGE-2 and 6-oxo-PGF-1 alpha synthesizing capacities were 4.0-, 3.4- and 2.5-fold higher, respectively, than in untreated, pregnant guinea-pigs on Day 15, and tended to be higher than in Day-15 non-pregnant guinea-pigs. Plasma progesterone concentrations were much lower in these 3 animals than in the other 9 treated with oestradiol, and also much lower than in untreated, pregnant guinea-pigs on Day 15.(ABSTRACT TRUNCATED AT 400 WORDS)