AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 6 882-R887, Copyright © 1983 by American Physiological Society
Umbilical glucose and lactate extractions during maternal hyperglycemia in sheep
S. S. Crandell, P. A. Palma and F. H. Morriss Jr
Umbilical glucose and lactate extractions were determined in previously
instrumented pregnant ewes into some of which D-glucose was infused to
produce graded levels of maternal hyperglycemia as great as 20 mM. While
fetal arterial glucose concentration continued to increase linearly as a
function of maternal arterial glucose concentration during maternal
hyperglycemia, the umbilical venoarterial difference in blood glucose
concentration did not, and umbilical glucose extraction approached a
plateau at approximately 0.063 mmol X min-1 X kg fetus-1 at maternal
glucose concentrations greater than approximately 8 mM. The observed
plateau in glucose extraction is consistent with saturation at high
maternal glucose concentrations of the carrier mechanism for transport of
glucose from the maternal to the fetal aspects of the trophoblast. The
observed value of the plateau in umbilical extraction of glucose is
slightly less than the maximum extraction predicted from previously
published equations for this species, but the maternal blood glucose
concentration at which the observed maximum occurred agrees closely with
the value predicted by those equations. Umbilical lactate extraction, 0.031
+/- 0.021 mmol X min-1 X kg fetus-1, was independent of maternal arterial
blood glucose and lactate concentrations and was independent of umbilical
glucose extraction.
