Journal
ZYGOTE
Volume 22, Issue 4, Pages 500-504Publisher
CAMBRIDGE UNIV PRESS
DOI: 10.1017/S096719941200072X
Keywords
Brilliant cresyl blue; Equine growth hormone; Horse; In vitro maturation; Oocyte competence
Funding
- Del Amo Program Grant (University of California, Davis and Universidad Complutense de Madrid, Spain)
- Coordination for the Improvement of Higher Education Personnel (CAPES), Brazil
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Immature oocytes synthesize a variety of proteins that include the enzyme glucose-6-phosphate dehydrogenase (G6PDH). Brilliant cresyl blue (BCB) is a vital blue dye that assesses intracellular activity of G6PDH, an indirect measure of oocyte maturation. The objective was to evaluate the BCB test as a criterion to assess developmental competence of equine oocytes and to determine if equine growth hormone (eGH) enhanced in vitro maturation (IVM) of equine oocyte. Cumulus-oocytes complexes (COCs) were recovered by aspirating follicles < 30 mm in diameter from abattoir-derived ovaries and were evaluated morphologically. Thereafter, COCs were exposed to BCB (26 mu M) for 90 min at 39 degrees C and selected based on the colour of their cytoplasm (BCB positive/BCB+ or BCB negative/BCB-). The COCs were allocated as follows: (a) IVM medium; (b) eGH group; (c) BCB-/IVM; (d) BCB+/IVM; (e) BCB/ eGH; and (f) BCB+/eGH. Then, COCs were cultured in vitro for 30 h, at 39 degrees C in a 5% CO2 humidified air atmosphere. Cumulus-free oocytes were incubated in 10 mu g/ml of bis-benzamide for 20 min at 39 degrees C and nuclear maturation was evaluated with epifluorescence microscopy. Of the 39 COCs selected morphologically and subjected to BCB staining, 18/39 (46.2%) were classified as BCB+ and 21/39 (53.8%) as BCB-(P > 0.05). Maturation was not affected significantly by BCB classification, but the maturation rate was higher for oocytes that had been exposed to exogenous eGH versus controls (16/28, 57.1% versus 8/26, 30.8%, P < 0.05). In the present study, the BCB test was not useful for predicting competent equine oocytes prior to IVM. However, eGH enhanced equine oocyte maturation in vitro.
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