Acosta Tomas J, Yoshizawa Nobuyuki, Ohtani Masayuki, Miyamoto Akio
Departamento de Fisiologia, Facultad de Ciencias Veterinarias, Universidad Nacional de Asuncion, San Lorenzo, Paraguay.
Biol Reprod. 2002 Mar;66(3):651-8. doi: 10.1095/biolreprod66.3.651.
One of the postulated main luteolytic actions of prostaglandin (PG) F(2 alpha) is to decrease ovarian blood flow. However, before Day 5 of the normal cycle, the corpus luteum (CL) is refractory to the luteolytic action of PGF(2 alpha). Therefore, we aimed to determine in detail the real-time changes in intraluteal blood flow after PGF(2 alpha) injection at the early and middle stages of the estrous cycle in the cow. Normally cycling cows at Day 4 (early CL, n = 5) or Days 10--12 (mid CL, n = 5) of the estrous cycle (estrus = Day 0) were examined by transrectal color and pulsed Doppler ultrasonography to determine the blood flow area, the time-averaged maximum velocity (TAMXV), and the volume of the CL after an i.m. injection of a PGF(2 alpha) analogue. Ultrasonographic examinations were carried out just before PG injection (0 h) and then at 0.5, 1, 2, 4, 8, 12, 24, and 48 h after the injection. Blood samples were collected at each of these times for progesterone (P) determination. The ratio of the colored area to a sectional plane at the maximum diameter of the CL was used as a quantitative index of the changes in blood flow within the luteal tissue. Blood flow within the midcycle CL initially increased (P < 0.05) at 0.5-2 h, decreased at 4 h to the same levels observed at 0 h, and then further decreased to a lower level from 8 h (P < 0.05) to 48 h (P < 0.001). Plasma P concentrations decreased (P < 0.05) from 4.7 +/- 0.5 ng/ml (0 h) to 0.6 +/- 0.2 ng/ml (24 h). The TAMXV and CL volume decreased at 8 h (P < 0.05) and further decreased (P < 0.001) from 12 to 24 h after PG injection, indicating structural luteolysis. These changes were not detected in the early CL, in which luteolysis did not occur. In the early CL, the blood flow gradually increased in parallel with the CL volume, plasma P concentration, and TAMXV from Day 4 to Day 6. The present results indicate that PGF(2 alpha) induces an acute blood flow increase followed by a decrease in the midcycle CL but not in the early CL. This transitory increase may trigger the luteolytic cascade. The lack of intraluteal vascular response to PG injection in the early CL appears to be directly correlated with the ability to be resistant to PG.
前列腺素（PG）F2α假定的主要黄体溶解作用之一是减少卵巢血流量。然而，在正常周期的第5天之前，黄体（CL）对PGF2α的黄体溶解作用具有抗性。因此，我们旨在详细确定在奶牛发情周期的早期和中期注射PGF2α后黄体内部血流量的实时变化。在发情周期的第4天（早期黄体，n = 5）或第10 - 12天（中期黄体，n = 5）（发情日 = 第0天）的正常发情奶牛通过经直肠彩色和脉冲多普勒超声检查来确定血流量面积、时间平均最大速度（TAMXV）以及肌肉注射PGF2α类似物后黄体的体积。在注射PG之前（0小时）以及注射后0.5、1、2、4、8、12、24和48小时进行超声检查。在这些时间点采集血样用于测定孕酮（P）。将黄体最大直径处的彩色面积与截面平面的比率用作黄体组织内血流量变化的定量指标。中期黄体的血流量在0.5 - 2小时时最初增加（P < 0.05），在4小时时降至与0小时时观察到的相同水平，然后从8小时（P < 0.05）到48小时（P < 0.001）进一步降至更低水平。血浆P浓度从4.7±0.5 ng/ml（0小时）降至0.6±0.2 ng/ml（24小时）（P < 0.05）。TAMXV和黄体体积在8小时时下降（P < 0.05），并且在注射PG后12至24小时进一步下降（P < 0.001），表明发生了结构性黄体溶解。在早期黄体中未检测到这些变化，早期黄体未发生黄体溶解。在早期黄体中，从第4天到第6天，血流量与黄体体积、血浆P浓度和TAMXV平行逐渐增加。目前的结果表明，PGF2α在中期黄体中诱导血流量先急性增加随后减少，但在早期黄体中并非如此。这种短暂的增加可能触发黄体溶解级联反应。早期黄体中对PG注射缺乏黄体内部血管反应似乎与对PG的抗性能力直接相关。
