Production of prostaglandin F 2α and estrogen by embryonal membranes and endometrium and metabolism of prostaglandin F 2α by embryonal membranes, endometrium and lung from gilts

Abstract

A 3 hr incubation of endometrium and embryonal membranes was used to assess potential contributions of these tissues to the prostaglandin F 2α (PGF 2α) and unconjugated estrogen (UE) present in the uteri of pregnant gilts. Metabolism of [ 3H]PGF 2α was determined during a 6 hr incubation of endometrium, lung and embryonal membranes to assess the contribution of these tissues in conversion of PGF 2α to less active forms during the estrous cycle and early pregnancy. Tissue was collected from 12 cyclic gilts on days 13, 16 or 19 and from 17 pregnant gilts on days 13, 16, 19 and 25 after the onset of estrus (day 0). Concentration of PGF 2α (ng/g of tissue) in incubation medium after incubation of endometrium at 37 C was 4- to 6-fold greater (P<.001) on days 16 and 19 for cyclic gilts than for pregnant gilts. Concentration of PGF 2α in medium after incubation of embryonal membranes recovered on days 13 and 16 was similar to that found after incubation of endometrium from cyclic gilts on days 16 and 19. Percentage of [ 3H]PGF 2α converted by endometrium and lung tissue to other metabolites (61.8 and 79.5%, respectively) did not differ significantly among days of the cycle or pregnancy. The percentage of [ 3H]PGF 2α metabolites recovered as [ 3H]13,14-dihydro-15-keto-PGF 2α (PGFM) for endometrium (50.3%) and for lung (64.6%) was not affected significantly by pregnancy status. Embryonal membranes recovered on days 13 and 16 converted more (P<.05) [ 3H]PGF 2α to other metabolites (%/μg of DNA) than embryonal membranes recovered on days 19 and 25, lung or endometrium. The % of [ 3H]PGF 2α metabolites recovered as [ 3H]PGFM for embryonal membranes increased (P<.05) from 37.4 on day 13 to 68.6 on day 25. Concentration of UE (ng/g of tissue) in medium after incubation of embryonal membranes from day 13 was about 100-fold greater than for endometrium. Concentration of UE and estrone sulfate (E 1SO 4) (ng/g of tissue) in medium after incubation was greater (P<.05) for endometrium from pregnant gilts on day 25 than that for all days of the cycle or pregnancy. Concentration of UE in medium after incubation of endometrium or embryonal membranes was not significantly affected by incubation treatment, but more E 1SO 4 accumulated in the presence of indomethacin (P<.01). These results indicate that endometrium from pregnant gilts produces less PGF 2α than that of cyclic gilts in vivo and this may contribute to the maintenance of corpora lutea. The high concentrations of PGF 2α and estradiol in uteri of pregnant gilts may originate from embryonal membranes and be converted to biologically less active forms before leaving the uterus.