2010 Volume 56 Issue 4 Pages 428-436
Administration of prostaglandin (PG) F2α in cattle during the mid-luteal phase (Days 8-12 of the estrous cycle) drastically reduces the plasma progesterone concentrations and the volume of the corpus luteum (CL). However, PGF2α does not induce luteolysis during the early luteal phase (up to Day 5 of the estrous cycle). To characterize the possible distinct difference in acute response to a luteolytic dose of PGF2α administration, we determined various mRNA expressions in the early and mid CL relating to angiogenesis, vasoactivation and PG-related factors at 30 min after PGF2α injection in cyclic cows. The experiments were conducted on Day 4 (early CL) and Days 10-12 (mid CL). Cows were either injected with 500 μg PGF2α analogue or saline as the control (early CL control, n=5; early CL PGF2α treated, n=5; mid CL control, n=5; mid CL PGF2α treated, n=7). Thirty min after injection of PGF2α or saline, the cows were ovariectomized transvaginally, and the CL tissues were collected from regions designated as the periphery and center of the CL. Administration of PGF2α up-regulated the mRNA expressions of angiogenic-related factors such as vascular endothelial growth factors, vasohibin, fibroblast growth factor 2 and insulin-like growth factor-II in the early CL, whereas PGF2α down-regulated these mRNA expressions in the mid CL. In the vasoactive factors, PGF2α stimulated the mRNA expressions of endothelin-1, angiotensin converting enzyme, endothelial nitric oxide synthase (NOS) and inducible NOS in the periphery area of the mid CL, but not in the early CL. However, PGF2α drastically down-regulated PGF2α receptor mRNA expression in both regions of the early and mid CL. The results indicated a clear difference in the acute action of PGF2α depending not only on the luteal phase (immature vs. mature) but also the region (periphery vs. center) within the CL at 30 min after PGF2α injection in the cow.
