The fate of the canine corpus luteum (CL) differs from that of other domestic species: beyond the extended luteal regression observed in both pregnant and non-pregnant cycles, active luteolysis is observed only in pregnant dogs. Luteal regression in the absence of pregnancy lacks a luteolytic trigger. The CL lifespan during pregnancy is around 60 days, as long as that of the cyclic CL. Although they are already available in the first half of diestrus, LH and especially prolactin (PRL) play a decisive luteotropic role from approximately day 25 post-ovulation onwards. Nevertheless, many locally-produced factors are orchestrated to ensure a fully functional CL, which in the bitch produces progesterone (P4), 17b-estradiol, and other local regulators. Recently, insulin has been described as another luteotropic factor in this species, able to increase glucose uptake in luteal cells and contribute to steroid biosynthesis. The locally-produced PGE2 is also a potent luteotropic factor in the first half of diestrus, promoting STAR expression, as are also proliferating, vasoactive- and immunomodulatory factors. These, in turn, all contribute to the formation and maintenance of the canine CL. Meanwhile PGF2a, produced by the utero-placental compartment, participates actively in triggering pre-partum luteolysis. Cytokines play different roles, either contributing as luteotropic or as acute inflammation molecules. So far, the one clinically most efficient mechanism of interrupting a pregnancy in the dog is to block P4 receptors, using an antigestagen (e.g., aglepristone) in the second half of diestrus. To enhance the chances of pregnancy, however, several luteotropic factors could be used.

中文翻译：

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影响犬黄体命运的因素：怀孕和未怀孕的潜在因素

犬黄体 (CL) 的命运与其他家养物种不同：除了在怀孕和非怀孕周期中观察到的黄体退化延长之外，仅在怀孕犬中观察到主动黄体溶解。在没有怀孕的情况下，黄体退化缺乏黄体溶解触发因素。怀孕期间的 CL 寿命约为 60 天，与循环 CL 的寿命一样长。尽管它们已经在发情期的前半段可用，但 LH 尤其是催乳素 (PRL) 从排卵后大约 25 天起就开始发挥决定性的促黄体作用。然而，许多本地产生的因素经过精心设计以确保功能齐全的 CL，它在母狗中产生黄体酮 (P4)、17b-雌二醇和其他本地调节剂。最近，胰岛素被描述为该物种的另一种促黄体因子，能够增加黄体细胞对葡萄糖的摄取并有助于类固醇的生物合成。本地生产的 PGE2 也是一种有效的促黄体因子，可促进 STAR 表达，以及增殖、血管活性和免疫调节因子。反过来，这些都有助于犬 CL 的形成和维持。同时，由子宫胎盘隔室产生的 PGF2a 积极参与触发产前黄体溶解。细胞因子扮演不同的角色，或者作为促黄体或作为急性炎症分子。到目前为止，一种临床上最有效的中断狗妊娠的机制是阻断 P4 受体，在发情的后半部分使用抗孕激素（例如，阿格列司酮）。然而，为了增加怀孕的机会，