Day 5 sheep embryos (late morulae and early blastocysts) were surgical
ly recovered from superovulated ewes. Groups of embryos (four to seven
) were incubated for 24 h at 39-degrees-C under humidified 5% CO2, 5%
O2, 90% N2 in 50-mul microdrops of a substrate-free synthetic oviduct
fluid (SOF) medium (12 mg ml-1 bovine serum albumin, m-SOF) containing
1.0 mM glucose and +/- 1.0 mM glutamine. Following incubation, embryo
s were washed in m-SOF and stored at -70-degrees-C until fractionation
. Embryos were fractionated into acid-soluble (glycogen/non-glycogen)
and acid-insoluble (desmoglycogen/non-glycogen) fractions. To further
characterise glucose carbon partitioning in the acid-soluble fraction,
carbohydrates were separated by high performance liquid chromatograph
y (HPLC). Incorporation of glucose into glycogen or desmoglycogen in p
ost-compaction sheep embryos was negligible. The presence of glutamine
tended to accelerate morphological development over the 24 h culture
period, but had no significant effect on glucose incorporation. Most g
lucose carbon was associated with the acid-soluble non-glycogen fracti
on. HPLC revealed that this was predominantly glucose (approximately 4
0%), in addition to other metabolic intermediates. It is concluded tha
t, unlike the mouse embryo, sheep embryos produce negligible glycogen
from exogenous glucose and that most of the glucose carbon incorporate
d in the embryo is in the form of low molecular weight metabolites or
unmetabolised glucose.