Purpose To evaluate associations of glucose-6-phosphate dehydrogenase (G6PDH)
activity in sheep oocytes with cytoplasmic lipid content, maturational competence,
developmental competence to the blastocyst stage, and gene expression of certain
Methods Before brilliant cresyl blue (BCB) staining test, oocytes were classified as
high, middle, and low cytoplasmic lipid content (HCLC, MCLC, and LCLC) and after the
test as having low or high G6PDH-activity (BCB+ and BCB-, respectively). After
maturation in vitro, a group of oocytes were subjected to IVF followed by in vitro
embryo culture and another group was used for evaluation of expression of candidate
Results The cleavage and blastosyst rates were lowest (P < 0.05) in LCLC group,
intermediate (P < 0.05) in MCLC group and highest (P < 0.05) in HCLC group. More
(P < 0.05) oocytes in HCLC group were BCB+, and higher (P < 0.05) maturation,
cleavage, and blastocyst rates were seen for BCB+ oocytes than the BCB- oocytes.
Our gene expression data indicated that mRNA transcript abundance of ITGB2, pZP3,
BMP15, and GDF9 genes were similar between BCB oocytes groups. However, the
expression of ATP1A1 was higher (P < 0.05) for BCB+ oocytes compared to BCBoocytes.
In addition, BAX transcript abundance was similar (P > 0.05) among BCB+,BCB-, and control groups, before and after maturation in vitro.
Conclusion Activity of G6PDH in sheep oocytes is highly associated with lipid content,
and compared with the morphological parameters, might be a more precise and
objective predictor for subsequent developmental competence in vitro.