Development and de novo protein synthetic activity of bovine embryos produced in vitro in different culture systems

Abstract

In vitro matured (IVM) and fertilized (IVF) putative Day 1 zygotes (Day 0 = IVF) were allocated randomly to culture in formulations based on Synthetic Oviduct Fluid (SOF) medium and identified on the basis of their contrasting principal supplements, which were 10% v/v steer serum (SS; n = 558) or 4 mg/mL crystalline BSA (SBSA; n = 531) or 3 mg/mL polyvinyl alcohol (SPVA; n = 607) in 9 replicates. SBSA and SPVA also contained 10 mug/mL non-essential amino acids, while the former was further supplemented with 20 muL/mL essential amino acids and the latter with 0.5 mmol/L sodium citrate and 5 ng/mL epidermal growth factor. Zygotes were cultured in 20 muL drops (4 zygotes per drop) until Day 8 in an atmosphere of 5% CO(2), 5% O(2) and 90% N(2) at 39 degreesC and droplets were renewed every 48 hours. The incidence of zygote cleavage was lower (P < 0.05) in SS (mean +/- SEM = 61 +/- 3%) than in SBSA (76 +/- 3%) but not in SPVA (72 +/- 4%) up to Day 3. The SPVA generated a lower yield of blastocysts on Day 7 (12 +/- 2%; P < 0.001) and by Day 8 (21 +/- 4%; P < 0.01) than did SS (33 +/- 3%; 40 +/- 3%) and SBSA (30 +/- 3%; 37 +/- 4%). Cell numbers (n) and diameters (d) of blastocysts on Day 8 were greater (P < 0.001; Replicates 1 to 5) in embryos from SBSA. (n, 156 +/- 9; d, 203 +/- 4 mum) than in those from SS (n, 81 +/- 4; d, 177 +/- 3 mum) and SPVA (n, 76 +/- 5; d, 167 +/- 3 mum). Embryos produced in SS incorporated less (3)H-phenylalanine into PCA-precipitable protein (replicates 6 to 9; log(10) dpm = 3.03 +/- 0.04) than did embryos cultured in SBSA (3.21 +/- 0.03; P < 0.001) or in SPVA (3.14 +/- 0.03; NS). In conclusion, blastocyst yield was poor in SPVA, but the embryos had metabolic activities similar to those of embryos produced in SBSA. Blastocyst yields from SS were not compromised but their capacity for de novo protein synthesis was reduced significantly. (C) 2001 by Elsevier Science Inc.