Contents volume 44

Abstract

This study was performed to determine the influence of insemination as well as treatment with human chorionic gonadotropin (hCG) and equine chorionic gonadotropin (eCG) on expression of the vascular endothelial growth factor (VEGF) system in porcine oviducts. In the first experiment, 10 gilts were assigned to 2 groups: cyclic (treated with phosphate-buffered saline; n = 5) and inseminated (n = 5). In experiment II, 15 gilts were assigned to 3 groups: inseminated (control; n = 5), induced ovulation and inseminated (750 IU eCG, 500 IU hCG; n = 5), and superovulated and inseminated (1500 IU eCG, 1000 IU hCG; n = 5). Oviducts (isthmus and ampulla) were collected 3 days after phosphate-buffered saline treatment (experiment I) or insemination. Blood samples were collected during slaughter for E2 (estradiol) and P4 (progesterone) analysis. Levels of messenger RNA (mRNA) of the VEGF system were analyzed by real-time polymerase chain reaction and protein by Western blot and E2 and P4 using radioimmunoassays. Insemination by itself decreased VEGF120 mRNA expression and VEGF-A protein level in the oviductal isthmus (P < 0.05) but did not alter VEGF164 mRNA. Expression of Flt-1 (c-fms-like tyrosine kinase VEGFR-1) mRNA increased in the isthmus of inseminated relative to cyclic gilts (P < 0.05), whereas KDR (fetal liver kinase-1 VEGFR-2) mRNA levels decreased in both the oviductal isthmus (P < 0.05) and ampulla (P < 0.001). Superovulation decreased VEGF120 and VEGF164 mRNA expression in the isthmus compared with the inseminated group (P < 0.05), and lowered protein levels of VEGF-A in the isthmus of both stimulated groups (P < 0.001). Expression of Flt-1 mRNA was affected by hCG and eCG treatment in both gonadotropin-stimulated groups in the isthmus as well as in the ampulla (P < 0.001) and protein levels in the ampulla of superovulated gilts (P < 0.05). Protein levels of KDR were reduced in the oviductal ampulla of gilts in both the induced ovulation and superovulated groups (P < 0.05). The concentrations of both E2 and P4 increased significantly in superovulated group of gilts (P < 0.01 and P < 0.05 for E2 and P4, respectively). Our study showed that insemination alone as well as ovarian stimulation affected the mRNA and protein profiles of the VEGF system in the porcine oviduct. Disrupted VEGF system expression may be crucial to many events occurring during the periovulatory period and consequently could lead to deprivation of VEGF-dependent factors that are necessary for proper fertilization, gamete transport, and embryo development.