Effects of Prostaglandin (PG) E1 or E2 (PGE1, PGE2) Intra-luteal Implants on Vascular Endothelial Growth Factor (VEGF) and Fibroblast Growth Factor-2 (FGF-2), and Angiopoietin 1 and 2 (ANG-1; ANG-2) Receptor: B-actin Ratio to Prevent Luteolysis in Cows.

Loss of progesterone secretion by the corpus luteum (CL) at the end of an estrous cycle is via uterine PGF2a secretion; however, PGF2a is not decreased during early pregnancy in ewes. Instead, the embryo imparts resistance to PGF2a during early pregnancy via increased uterine PGE1 and PGE2. Intra-uterine administration of PGE1 or PGE2 every 4 hr prevents spontaneous or induced luteolysis in ewes. PGE1 prevents luteolysis in ewes and cows by inhibiting the decrease in CL: 1) weight, 2) P4 secretion, 3) CL mRNA for LH receptors, 4) occupied and unoccupied LH receptors, and 5) altering CL prostanoid receptor mRNA (Y. Weems et al., Prostaglandins & Other Lipid Mediators, 91:42, 2010; Weems et al. Proc. Amer. Soc. Anim. Sci., 2009; Proc. SSR, 2010). The objective of this study was to determine effects of intra-luteal implants of PGE1 or PGE2 on VEGF, FGF-2, ANG-1, and ANG-2:B actin ratio of Brahman or Angus cows. Cows received intra-luteal implants containing Vehicle, PGE1, or PGE2 from D-13 to D-19 post-estrus via a flank laparotomy. CL were recovered on D-19, weighed, quartered, and frozen in liquid nitrogen until analysis for VEGF, FGF-2, ANG-1, and ANG-2:B-actin ratio by SDS-PAGE, Western Blot, Image Scanner, and Image QuantTL. D-13 Angus CL weights served as pre-luteolytic controls. CL angiogenic receptors were analyzed by GLM for CRD and REST-2008 software and LS means were compared to controls. Data for VEGF were not (P>0.05) affected by breed, treatment, or day. FGF-2 was affected (P<0.05) by breed and treatment. PGE1 or PGE2 increased (P<0.05) FGF-2 compared to D-13 or D-19 Angus controls, while PGE1 or PGE2 decreased (P<0.05) FGF-2 compared to D-19 Brahman controls. There was no effect (P>0.05) of PGE1 or PGE2 on ANG-1 of Angus D-13 or D-19 controls, but ANG-1 was decreased (P<0.05) by PGE1 or PGE2 in Brahman cows compared to D-19 Brahman controls. ANG-2 was increased (P<0.05) in D-19 Vehicle controls, which was prevented (P<0.05) by PGE1, but not (P>0.05) by PGE2 in Angus cows. There was no effect of PGE1 or PGE2 on ANG-2 in Brahman cows. PGE1 or PGE2 may alter cow CL FGF-2, ANG-1, or ANG-2, but not VEGF to prevent luteolysis.