University of Wisconsin-Madison, Madison, Wisconsin, USA; University of São Paulo, Piracicaba, Brazil.
University of Wisconsin-Madison, Madison, Wisconsin, USA.
Theriogenology. 2014 Feb;81(3):389-95. doi: 10.1016/j.theriogenology.2013.10.009. Epub 2013 Oct 18.
The early corpus luteum (CL) (before Day 6) does not regress after a single PGF2α treatment. We hypothesized that increasing PGF2α dose or number of treatments would allow regression of the early CL (Day 5). Nonlactating Holstein cows (N = 22) were synchronized using the Ovsynch protocol. On Day 5 (Day 0 = second GnRH treatment), cows were assigned to: (1) control (N = 5): no further treatment; (2) 1PGF (N = 6): one dose of 25 mg PGF2α; (3) 2PGF (N = 5): two doses of 25 mg PGF2α (50 mg) given 8 hours apart (second PGF2α on Day 5 at the same time as the other PGF2α treatments); (4) DPGF (N = 6): double dose of 25 mg PGF2α (50 mg) given on Day 5. Blood samples were collected to monitor progesterone (P4) profiles in two periods. In the first period (0 to 24 hours), there were effects of treatment (P = 0.01), time (P < 0.01), and an interaction of treatment and time (P = 0.02). Group 1PGF versus control was different only at 12 hours (P = 0.02). Cows treated with DPGF were different than control at 4 hours (P = 0.04), 12 hours (P < 0.01), and 24 hours (P < 0.01). Only cows treated with 2PGF had lower P4 than control during the entire period and low P4 (0.37 ± 0.17 ng/mL) at 24 hours, usually indicative of luteolysis. In the second period (Day 5 to 15 of the cycle), there were effects of treatment (P < 0.01), time (P < 0.01), and interaction of treatment and time (P = 0.002). Group 1PGF was not different than control from Day 5 to 13 and P4 was greater than control on Day 14 (P = 0.01) and 15 (P < 0.01). Circulating P4 in DPGF cows was lower than control from Day 7 (P = 0.05) through 12 (P < 0.01). Likewise, there were differences between control and 2PGF from Day 7 to 13, but not on Day 14 and 15. On Day 15, all PGF2α-treated groups had circulating P4 consistent with an active CL. Ultrasound evaluation confirmed that no CL from any group completely regressed during the experiment and no new ovulations occurred to account for functional CL later in cycle. In summary, a double dose of PGF2α (twice on Day 5 or 8 hours apart) can dramatically decrease P4, consistent with classical definitions of luteolysis; however, these CL recover and become fully functional. Thus, the Day 5 CL of mature Holstein cows do not regress even to two doses of PGF2α.
早期黄体（CL）（第 6 天之前）在单次 PGF2α 处理后不会退化。我们假设增加 PGF2α 剂量或处理次数会允许早期 CL（第 5 天）的退化。非泌乳荷斯坦奶牛（N=22）使用 Ovsynch 方案同步。在第 5 天（第 0 天=第二次 GnRH 处理），奶牛被分配到：（1）对照组（N=5）：无进一步处理；（2）1PGF（N=6）：一次 25mg PGF2α 剂量；（3）2PGF（N=5）：两次 25mg PGF2α（50mg）剂量，间隔 8 小时（第二次 PGF2α 在第 5 天与其他 PGF2α 处理同时进行）；（4）DPGF（N=6）：50mg 双倍剂量 PGF2α（25mg）在第 5 天给予。采集血液样本以监测两个时期的孕激素（P4）谱。在第一个时期（0 至 24 小时），处理（P=0.01）、时间（P<0.01）和处理与时间的相互作用（P=0.02）有影响。与对照组相比，1PGF 组仅在 12 小时（P=0.02）时不同。DPGF 处理的奶牛在 4 小时（P=0.04）、12 小时（P<0.01）和 24 小时（P<0.01）时与对照组不同。只有 2PGF 处理的奶牛在整个时期的 P4 水平低于对照组，并且在 24 小时时的 P4 水平低（0.37±0.17ng/mL），通常表明黄体溶解。在第二个时期（周期第 5 至 15 天），处理（P<0.01）、时间（P<0.01）和处理与时间的相互作用（P=0.002）有影响。1PGF 组与对照组在第 5 至 13 天没有区别，并且在第 14 天（P=0.01）和第 15 天（P<0.01）时 P4 高于对照组。DPGF 奶牛的循环 P4 从第 7 天（P=0.05）到第 12 天（P<0.01）低于对照组。同样，对照组与 2PGF 组在第 7 天至 13 天之间存在差异，但在第 14 天和第 15 天没有差异。在第 15 天，所有 PGF2α 处理组的循环 P4 与活跃的 CL 一致。超声评估证实，在实验过程中，没有任何一组的 CL 完全退化，也没有新的排卵发生以解释周期后期的功能性 CL。总之，PGF2α 的双倍剂量（第 5 天两次或间隔 8 小时）可以显著降低 P4，与经典的黄体溶解定义一致；然而，这些 CL 会恢复并变得完全功能。因此，成熟荷斯坦奶牛的第 5 天 CL 即使接受两次 PGF2α 处理也不会退化。
