Flint A P, Burton R D, Gadsby J E, Saunders P T, Heap R B
Ciba Found Symp. 1978(64):209-38. doi: 10.1002/9780470720479.ch10.
The maternal recognition of pregnancy takes a number of forms in different species; among the eutherian mammals the maintenance of luteal function and cessation of oestrous or menstrual cycles is an important event in early pregnancy. In the pig the embryos signal their presence in the uterus between Days 10 and 12 post coitum; this time corresponds to the onset of blastocyst synthesis of oestrogens, which are luteotrophic in this species, and it has been suggested that oestrogens may constitute an embryonic signal responsible for maintained luteal function in pregnancy. Although oestrone sulphate, which is formed from oestrogens of embryonic origin by uterine sulphotransferase, has been found in the maternal circulation in high concentrations after Day 15 p.c., its appearance is late relative to the time of maternal recognition of pregnancy. Therefore an alternative mechanism has been sought. The recent finding that oestradiol is capable of reducing uterine prostaglandin F2 alpha secretion (i.e. acting as an antiluteolysin), and that it is present in uterine venous blood as early as Day 12 p.c. in pregnant pigs, suggests a mechanism whereby blastocyst oestrogens may be capable of influencing luteal function.
在不同物种中，母体对妊娠的识别有多种形式；在真兽亚纲哺乳动物中，黄体功能的维持以及发情周期或月经周期的停止是早期妊娠中的一个重要事件。在猪中，胚胎在交配后第10至12天向子宫发出它们存在的信号；这个时间与囊胚合成雌激素的开始相对应，雌激素在该物种中具有促黄体作用，有人提出雌激素可能构成一种胚胎信号，负责维持妊娠期间的黄体功能。虽然在妊娠第15天后，由胚胎来源的雌激素经子宫硫酸转移酶形成的硫酸雌酮已在母体循环中被发现其浓度很高，但其出现时间相对于母体识别妊娠的时间较晚。因此，人们一直在寻找另一种机制。最近的研究发现，雌二醇能够减少子宫前列腺素F2α的分泌（即起到抗溶黄体素的作用），并且在妊娠母猪中，早在妊娠第12天它就存在于子宫静脉血中，这提示了一种囊胚雌激素可能影响黄体功能的机制。
