During pregnancy, as conceptus size and nutrient requirements increase, placental transfer capacity must also increase.
16
This is achieved through a variety of mechanisms,
including increasing placental surface area for nutrient transfer,
thinning of the trophoblast barrier, an increase in fetal capillary
surface area, increases in placental nutrient transporter abundance and modulation of placental bloodflow.
17,18
A key example
is the regulation of placental transfer capacity for glucose, the
major substrate for fetal oxidative metabolism.19
Glucose is
transported across the placenta by facilitated diffusion down a
concentration gradient. The development of a degree of maternal
insulin resistance during midelate pregnancy aids fetal glucose
supply by increasing the magnitude of the gradient. In addition,
data from in-vitro studies on human placentae suggest that there
is a redistribution of the expression of insulin receptors
throughout gestation, with increased expression on fetal surfaces in late gestation.
2
During pregnancy, as conceptus size and nutrient requirements increase, placental transfer capacity must also increase.
16
This is achieved through a variety of mechanisms,
including increasing placental surface area for nutrient transfer,
thinning of the trophoblast barrier, an increase in fetal capillary
surface area, increases in placental nutrient transporter abundance and modulation of placental bloodflow.
17,18
A key example
is the regulation of placental transfer capacity for glucose, the
major substrate for fetal oxidative metabolism.19
Glucose is
transported across the placenta by facilitated diffusion down a
concentration gradient. The development of a degree of maternal
insulin resistance during midelate pregnancy aids fetal glucose
supply by increasing the magnitude of the gradient. In addition,
data from in-vitro studies on human placentae suggest that there
is a redistribution of the expression of insulin receptors
throughout gestation, with increased expression on fetal surfaces in late gestation.
2
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