| Abstrakt: |
The objective of this study was to determine the effect of embryo production systems on the expression of insulin-like growth factor (IGF)-II mRNA in fetal bovine tissues at Day 70 of gestation (63 days after transfer). Oocytes aspirated from ovaries of Holstein cows were matured and fertilized in vitro. Zygotes were cultured in either tissue culture medium (TCM)-199 + 10% estrous cow serum (ECS; in vitro-produced with serum [IVPS]) or TCM-199 + 1% BSA (in vitro-produced with serum restriction [IVPSR]). At 72 h postinsemination, IVPSR embryos were transferred into fresh TCM-199 + 10% ECS whereas IVPS embryos had fresh medium replaced. All embryos were cultured for an additional 96 h. In vivo-produced embryos were harvested from superovulated Holstein cows (multiple ovulations [MO]). Grade 1 blastocysts from all groups were transferred singly into Angus heifers. At Day 70 of gestation, fetuses (n = 14, 13, and 11 for MO, IVPS, and IVPSR, respectively) were collected; liver and skeletal muscle samples were snap frozen, and whole-cell RNA (wcRNA) was extracted. Levels of IGF-II mRNA were determined by RNase protection assay and quantified relative to 18S rRNA (mean arbitrary units ± SEM). WcRNA from adult and Day 90 fetal bovine liver were used as controls. Adult liver contained 9-fold less IGF-II mRNA than liver from Day 90 fetuses (P< 0.05). Fetal livers of males originating from IVPS and IVPSR groups possessed approximately 2-fold greater levels of mRNA for IGF-II than those from MO males (0.25 ± 0.07, 0.33 ± 0.04, and 0.14 ± 0.03, respectively; P< 0.05). Levels of mRNA for IGF-II tended to be lower (P= 0.07) in skeletal muscle of fetuses originating from the IVPSR group (0.043 ± 0.005) compared to MO controls (0.070 ± 0.008). In conclusion, at Day 70 of gestation, fetuses originating from in vitro production systems possessed altered levels of IGF-II mRNA in both liver and skeletal muscle. |
