Rg. Wales et Ee. Waugh, OXIDATION OF [U-C-14]ACETATE BY THE SHEEP CONCEPTUS BETWEEN DAYS 13 AND 19 OF PREGNANCY, Reproduction, fertility and development, 5(2), 1993, pp. 201-208
Acetate metabolism by the sheep conceptus was assessed by measuring CO
2 production during a 2.5-h incubation of embryos and samples of the e
xtraembryonic membranes in HEPES-bufferd media containing 1.12 mM [U-C
-14]acetate. The rate of oxidation of acetate by embryonic tissue show
ed little change between Days 13 and 15 of pregnancy but greatly decre
ased by Days 17 and 19. By contrast, oxidation of the substrate by the
trophoblast increased substantially with development and was rive tim
es the early rate by Day 19. Oxidation of acetate by the yolk sac also
increased 4-fold between Days 17 and 19. The addition of glucose to i
ncubations of extraembryonic membranes resulted in some reduction in t
he oxidation of acetate by the yolk sac and allantois but had little e
ffect on the trophoblast. At Days 13 and 15, the rate of oxidation of
acetate by the embryonic disc was 6-7 times that by the trophoblast. A
s development progressed, this situation was reversed and by Day 19 th
e trophoblast metabolized more than five times the amount of acetate p
er mug than did the Day-19 embryo. Although acetate metabolism by yolk
sac and allantois on Day 17 was low, its metabolism by the yolk sac i
ncreased to values similar to those for the trophoblast at Day 19 but
its utilization by the allantoic membrane remained low. Comparison of
the estimates of ATP generated from acetate by these tissue with those
published for glucose demonstrates that acetate is much less effectiv
e than glucose for the provision of metabolic energy.