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Effects of D ‐glucose concentration, D ‐fructose, and inhibitors of enzymes of the pentose phosphate pathway on the development and sex ratio of bovine blastocysts
Author(s) -
Kimura Koji,
Spate L.D.,
Green M.P.,
Roberts R. Michael
Publication year - 2005
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.20342
Subject(s) - blastocyst , biology , embryo , medicine , endocrinology , pentose phosphate pathway , fructose , insemination , glucose uptake , andrology , glucose transporter , embryo culture , carbohydrate metabolism , glut1 , embryogenesis , metabolism , biochemistry , glycolysis , pregnancy , genetics , insulin
D ‐glucose at 5.6 mM reduces the progression of in vitro‐produced (IVP) bovine embryos from the morula to the blastocyst stage and skews sex ratio towards males. Possibly, the presence of two transcriptionally active X‐chromosomes compromises female embryo development through imbalance in glucose metabolism. Here, we have determined the threshold of embryo sensitivity to glucose, whether substitution of D ‐fructose for glucose reduces the selective loss of female embryos, and whether inhibition of an X‐linked gene product, glucose 6‐phosphate dehydrogenase (G6PD), normalizes sex ratio among bovine blastocysts. IVP zygotes were cultured in glucose‐free medium to 72 hr post‐insemination, at which time 8‐cell embryos were selected for treatment and cultured until 144 hr post‐insemination. Addition of 4 mM glucose at the 8‐cell stage reduced ( P < 0.05) the number of blastocyst that formed, whereas 2.5 and 1 mM glucose had no effect. Sex ratio in the presence of 4 and 2.5 mM glucose differed significantly from 0.5, while 1 mM glucose had no effect. D ‐fructose (5.6 mM) did not compromise development to blastocyst and did not alter the sex ratio of blastocysts that formed. When G6PD inhibitors (dehydroepiandrosterone: DHEA and 6‐aminonicotinamide: 6‐AN), which effectively inhibit the reduction of the NADPH‐sensitive dye, brilliant cresyl blue (BCB) in bovine morulae, were added to the culture medium containing 4 mM glucose, embryo development was moderately reduced, but sex ratio skewing was corrected (with 6‐AN) or lowered (with DHEA). In conclusion, glucose above 2.5 mM impairs bovine embryo development and increases sex ratio, most likely as a result of increased pentose‐phosphate (PP) pathway activity in female embryos. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.