| Luteolysis and the prevention of luteolysis are two important events in the cyclic and pregnant cow. In the pregnant animal, interferon- t (IFN- t ), secreted from the embryo, inhibits PG synthesis. We hypothesized that (1) steroid hormones and IFN- t have differential effects on the different endometrial cell types, (2) steroid hormones, OT and IFN- t act on the PG synthetic pathway, in particular regulating cyclooxygenase-2 (COX-2) and PGF synthase (PGFS) expression. The objectives of this study were to establish an appropriate primary endometrial cell culture system which could respond to steroid hormones, OT and IFN- t to examine the effect of steroid hormones on the receptors for E2 and P4, and to study the mechanisms by which the embryo modifies the ratio of PGF2a to PGE2.; The effects of steroid hormones on proliferation and morphology of endometrial cells were first examined. Addition of P4 altered the morphology of stromal cells. E2 and P4 increased the proliferation (P < 0.001) and decreased the protein to DNA ratios in stromal cells during the first 4 days. In contrast, the morphology of epithelial cells was riot influenced by the addition of steroids.; The effects of steroid hormones on their receptor numbers was determined. Cells were cultured for 4 or 8 days in medium alone or with E2, P4 or E2+P4. Saturation analysis showed that specific binding of both 16 a -Ethyl-21-hydroxy-19-nor (6,7-3H) pregn-4-ene-3,20-dione ([3H] ORG 2058) and [3H] E2 to epithelial and stromal cells exhibited high affinities. In the stromal cells, E2 increased E2 receptor (ER) and P4 receptor (PR) numbers after 4 days' culture (p < 0.01) in a dose- and time-dependent manner.; The effects of steroid hormones and recombinant bovine IFN- t (rbIFN- t ) on PG production and COX-2 and PGFS gene expression were investigated. E2 decreased both PGF2a and PGE2 whereas P4 increased PGF2a secretion in epithelial cells. Steroid hormones had no effect on PG production in stromal cells. rbIFN- t attenuated both PGF2a and PGE2 production in epithelial cells and enhanced their production, and the ratio of PGE2 to PGF2a , in stromal cells.; The effect of rbIFN- t on OT receptor (OTR) number, OT-induced PG production, COX-2 and PGFS expression in cultured endometrial epithelial cells was investigated. Confluent epithelial cells were incubated in the presence or absence of either 100 ng/ml OT or OT plus 100 ng/ml rbIFN- t for 3, 6, 12 and 24 h. rbIFN- t inhibited the OT-induced PG production and reduced OTR binding.; In conclusion, our results show that E2 and P4 have differential effects on the regulation of proliferation, morphology, receptor number, and PG secretion in the different endometrial cell populations. In vitro, IFN- t has a dual mechanism in the prevention of luteolysis. It stimulates the secretion of the luteoprotective agent, PGE2, by stromal cell, and inhibits the production of the luteolysin, PGF2a , by epithelial cells. (Abstract shortened by UMI.)... |
