Accumulating evidence suggests that uterine luminal fluids contain a variety of polypeptide growth factors and cytokines that, it is speculated, have roles in the development, growth and differentiation of the uterus and, during pregnancy, in the growth and survival of the embryo. Although epidermal growth factor (EGF) has previously been identified by radioimmunoassay and immunohistochemistry in the pig uterus, there have been no detailed studies of the secreted EGF protein. EGF was therefore purified from uterine flushings and uterine fluids of nonpregnant pigs of mixed breed using a variety of ion-exchange chromatography steps. Uterine flushings and fluids contained an anionic factor(s) that at 4 degrees C competed with 125I-labelled mouse EGF for binding to EGF receptors on an endometrial carcinoma cell line and stimulated DNA synthesis in Balb/c mouse 3T3 fibroblasts. As analysed by gel filtration, uterine fluids contained a 3-6 kDa factor that stimulated 3T3 cell DNA synthesis and was a competitor of cellular 125I-labelled EGF binding. Gel filtration further revealed that uterine flushings and fluids contained, respectively, 45 kDa and 40-70 kDa moieties that were mitogenic and that bound to the EGF receptor. SDS-PAGE and western blotting using an antiserum specific for pig EGF revealed immunoreactive forms of EGF of approximately 25 kDa in partially purified uterine flushings. It is concluded that uterine secretory EGF occurs, at least in part, as high molecular mass proteins. The ability of these high molecular mass EGFs to bind to and activate the EGF receptor suggests that they may be authentic ligands for the EGF receptor in utero.

To establish the efficient cytoplasmic microinjection system in the porcine embryos, pEGFP-N1 plasmid were microinjected into porcine parthenogenetic (PA) and in vitro-fertilized (IVF) embryos to investigate the optimal injection time, volume, and concentration. In experiment 1, to investigate the optimal injection time, development rates were compared among groups of 4 different time durations (2, 4, 6, and 8 hours) in the PA and IVF embryos with time point after activation and sperm removal, respectively. There were no significant differences (P < 0.05) between the 4 groups regarding the cleavage rates. However, there were significant differences (P < 0.05) in development to the blastocysts (4.4, 8.9, 3.9, 0.6%) and GFP expression in blastocysts (1.3, 5.7, 2.3, 0.0%), which was injected after postactivation of 4 hours compared with another 3 groups. The IVF embryos injected after 2 and 4 hours expressed GFP significantly higher than the other two groups, which injected at 6 and 8 hours (P < 0.05). In experiment 2, EGFP-N1 with 2 different concentrations (20 and 50 ng μL–1) was injected in the PA and IVF embryos to investigate the optimal concentration. In PA embryos, there were significant differences in 20 ng μL–1-injected embryos, which had higher cleavage (58.8 v. 41.9%) than blastocysts (13.0 v. 11.1%) and GFP expression rates (P < 0.05). In IVF embryos, GFP were expressed only in 20 ng μL–1 embryos, GFP (4.2%) in the blastocysts showed no significant difference in the cleavage (77.3 v. 64.7%) and blastocyst rates (26.4 v. 23.5%). In experiment 3, three different volumes (5, 10, and 20 pL) were microinjected into porcine embryos to determine the most appropriate volume. Out of 3 groups, significantly higher development rates of cleavage (68.3, 58.0, 29.3%), blastocysts (11.7, 12.7, 0.5%), and GFP-expressed blastocysts (2.9, 7.8, 0.0%) were shown in the 10-pL group (P < 0.05). In conclusion, these results imply that a 20 ng μL–1 concentration, 10 pL of volume, injection 4 hours after activation for PA embryos, as well as injection 2 and 4 hours after sperm removal, a 20 ng μL–1 concentration, and 10 pL of volume for IVF embryos were more effective cytoplasmic microinjection conditions.