Signal transduction systems within the bovine uterine endometrium that regulate prostaglandin secretion for maintenance of pregnancy.

摘要

Communication between conceptus and maternal unit is important for establishment of pregnancy. Objectives of this dissertation were: (1) to evaluate effect of pregnancy and administration of recombinant bovine somatotropin (bST) on expression of steroid hormone and oxytocin receptors, and genes related to biosynthesis of prostaglandins, such as PG H Synthase (S)-2 (PGHS-2), PGES and PGFS, and (2) to elucidate the signal transduction pathways related to synthesis of PGF2alpha and examine the effects of IFN-tau on these signal transduction systems using a bovine endometrial (BEND) cell line. Endometrial tissues were collected from cows at Day 17 after estrus. Pregnancy status was determined by presence of a conceptus in uterine flushes.; Pregnancy reduced steady state concentrations of Estrogen Receptor alpha (ERalpha) mRNA and protein. Treatment with bST increased steady state concentrations of oxytocin receptor (OTR) and progesterone receptor (PR) mRNAs and ERalpha protein in endometrium. Both pregnancy and treatment with bST failed to alter steady state concentrations of endometrial PGHS-2, PGES, and PGFS mRNAs at Day 17 of the estrous cycle. However, bST induced PGHS-2 protein expression. Increased immunohistochemical staining in the luminal epithelium was detected for ERalpha protein but not for PGHS-2 protein in cyclic cows. Phorbol 12, 13-dibutyrate (PdBu) stimulated secretion of PGF2alpha, and IFN-tau reduced PGF2alpha secretion in primary endometrial epithelial cells from cyclic cows at Day 17.; Treatment of BEND cells with PdBu induced and concurrent addition of IFN-tau reduced expression OF PGHS-2 mRNA, PGES mRNA, PGHS-2 protein and secretion of PGF2alpha and PGE2 after 6 h of treatment. In BEND cells, PdBu induces protein kinase C (PKC) activation which is inhibited by a specific PKC inhibitor (GF109203X). The PKC isotypes alpha, beta, gamma, and iota were identified in BEND cells. Among these isotypes, the total amount of cellular PKCalpha was reduced in response to PdBu and further decreased by concurrent treatment with IFN-tau. The PdBu-stimulated secretion of PGF2alpha is dependent on protein synthesis, since cycloheximide completely inhibited the response. The PdBu-induced expression of PGHS-2 mRNA is dependent on activation of p38 MAPK to sustain stability of the mRNA. Inhibition of p38 MAPK with a specific inhibitor SB203580 increases turnover of PGHS-2 mRNA in cells pretreated with PdBu for 3 h before addition of the inhibitor. Similarly, IFN-tau also increased PGHS-2 mRNA turnover. (Abstract shortened by UMI.)