Fetomaternal transfer of glucose analogues by sheep placenta
Stacey, T.E.; Weedon, A.P.; Haworth, C.; Ward, R.H.; Boyd, R.D.
American Journal of Physiology 234(1): E32-E37
1978
ISSN/ISBN: 0002-9513 PMID: 623245 Document Number: 132927
Steady-state permeability of the placenta to radiolabeled 3-O-methyl-D-glucopyranose (3MeG), .alpha.-methyl-D-glucopyranoside (AMG) and D-xylose was measured in chronically catheterized conscious sheep near term. Fetomaternal flux was calculated by application of Fick's principle to uterine circulation after injection to the fetus. At a fetal glucose concentration of 10.2 .+-. 1.25 mM, permeability of 3MeG was half the maximal value of 59.8 .+-. 11.2 ml/min found by extrapolation to 0 glucose concentration. Permeability to 3MeG was considerably greater than was compatible with restricted diffusion, which together with the competitive effect of D-glucose suggests a carrier-mediated transfer mechanism. Permeability to AMG was < 0.1 ml/min. The specificity pattern of sugar transport from the fetal side of the sheep placenta was different from that reported for gut lumen or kidney tubule in other species. D-Xylose was not metabolically inert after its injection into the fetal lamb.