Ziecik A J, Waclawik A, Bogacki M
Institute of Animal Reproduction and Food Research of Polish Academy of Sciences, Tuwima 10, Olsztyn, Poland.
Exp Clin Endocrinol Diabetes. 2008 Jul;116(7):443-9. doi: 10.1055/s-2008-1042405. Epub 2008 May 16.
Establishment of pregnancy in pigs requires estrogen secretion by the conceptus. The developmental changes of embryo before implantation and embryo-uterine cross talk are dependent on various biological molecules secreted by the endometrium and conceptus. An integral part of maternal recognition of pregnancy seems to be also the lipid signaling system consisting of prostaglandin (PG) F2 alpha and E2 and/or lysophosphatic acid (LPA). The downstream enzymes in PG synthesis pathway are: microsomal PGE synthase-1 (mPGES-1), PGF synthase (PGFS) and prostaglandin 9-ketoreductase/carbonyl reductase (CBR1) which catalyzes conversion of PGE 2 into PGF2 alpha. In contrast to mPGES-1, endometrial PGFS is highly increased on days 13-15 similarly as CBR1 on days 16-17 of the estrous cycle. Potential mechanism by which a conceptus inhibits luteolysis is changing the PGE2/PGF2 alpha ratio in favor of PGE2. It may be result of high expression of mPGES-1 in trophoblast and endometrium on days 10-13 of pregnancy and simultaneously the down-regulation of PGFS and CBR1 in conceptuses during this period. The conceptus can alter expression of endometrial CBR1 to modulate the PGE2/PGF2 alpha ratio in the uterus during the maternal recognition of pregnancy. High expression of conceptus and endometrial terminal PG synthases and CBR1 after initiation of blastocyst attachment suggest their involvement in early placentation. The higher LPA3 receptor mRNA expression during the early pregnancy compared to corresponding period of estrous cycle could indicate an important role of LPA and its receptor during the peri-implantation stage of pregnancy in pigs. Above results suggest that the lipid signaling system is an integral part of establishment and maintenance of pregnancy in the pig.
猪的妊娠建立需要着床前胚胎分泌雌激素。着床前胚胎的发育变化以及胚胎与子宫的相互作用依赖于子宫内膜和胚胎分泌的各种生物分子。母体对妊娠的识别似乎还离不开由前列腺素（PG）F2α、E2和/或溶血磷脂酸（LPA）组成的脂质信号系统。PG合成途径中的下游酶包括：微粒体PGE合酶-1（mPGES-1）、PGF合酶（PGFS）以及催化PGE2转化为PGF2α的前列腺素9-酮还原酶/羰基还原酶（CBR1）。与mPGES-1不同，在发情周期的第13至15天，子宫内膜PGFS显著增加，CBR1在第16至17天也有类似变化。胚胎抑制黄体溶解的潜在机制是改变PGE2/PGF2α的比例，使其更有利于PGE2。这可能是由于在妊娠第10至13天，滋养层和子宫内膜中mPGES-1高表达，同时在此期间胚胎中PGFS和CBR1下调。在母体识别妊娠期间，胚胎可改变子宫内膜CBR1的表达，以调节子宫内的PGE2/PGF2α比例。囊胚着床后，胚胎和子宫内膜末端PG合酶及CBR1的高表达表明它们参与了早期胎盘形成。与发情周期相应阶段相比，妊娠早期LPA3受体mRNA表达更高，这表明LPA及其受体在猪妊娠植入前期发挥着重要作用。上述结果表明，脂质信号系统是猪妊娠建立和维持的一个重要组成部分。
