Effect of Insulin, Transferrin and Platelet-Derived Growth Factor Supplemented to Synthetic Oviduct Fluid Medium on In Vitro Development of Bovine Embryos Matured and Fertilized In Vitro

합성난관배양액에 첨가된 Insulin, Transferrin 및 Platelet-Derived Growth Factor (PDGF)가 소 수정란의 체외발육에 미치는 영향

In vitro development of bovine embryos is affected by many factors such as energy substrates, amino acids, and some growth factors. It has been reported that mRNA of insulin, PDGF and their receptors are detected in cow embryos, and that some chelating agents such as EDTA and transferrin have beneficial role on mouse and bovine embryos. The author hypothesized that insulin, transferrin arid PDGF added to a culture medium increase in vitro development of bovine embryos by chelating toxic substance(s) or increasing cell growth and metabolism. Immature oocytes from slaughtered ovaries of Holstein cows and heifers were matured for 24 hours in a TCM199 containing 10% fetal calf serum, FSH, LH and estradiol with granulosa cells in vitro. Matured oocytes were coincubated with sperm for 30 hours in a modified Tyrode's medium (IVF). Embryos cleaved to 2- to 4-cell at 30 hours after IVF were selected and cultured in a 30-$\mu$l drop of a synthetic oviduct fluid medium (SOFM) containing 0.8% BSA, Minimum Essential Medium essential and non-essential amino acids, and insulin, transferrin or PDGF for 9 days. Supplementation of a SOFM with insulin, and /or transferrin did not increase develop-mental rate to expanding and hatching blastocyst of 2- to 4-cell bovine embryos compared with control. The highest developmental rate to hatching blastocyst was shown when PDGF was added at the concentration of 10 ng /ml among the supplementing doses tested in the present study (p<0.05). Addition of PDGF without insulin to a SOFM could not increase embrye development, but combined addition of PDGF with insulin significantly increased (p<0.05) embryo development to hatching blastocyst (50%) compared with control (38%). In conclusion, insulin and PDGF supplemented to a SOFM may act synergistically and have beneficial effect on in vitro development of 2- to 4-cell bovine embryos matured and fertilized in vitro.