AJP - Endocrinology and Metabolism, Vol 243, Issue 3 246-E250, Copyright © 1982 by American Physiological Society
Increased fetal insulin receptors and changes in membrane fluidity and lipid composition
N. D. Neufeld and L. Corbo
Fetal tissues exposed to hyperinsulinemia in utero have significantly
greater numbers of insulin receptors than do those of controls. We have
studied this upregulation phenomenon using crude microsomal membranes from
fetal rabbit litters exposed to varying degrees of hyperinsulinemia in
diabetic pregnant rabbits. We have observed that insulin binding capacity
of membranes increased directly with the severity of maternal diabetes,
ranging from 8.5 ng in controls to 44.6 ng insulin/mg membrane protein in
offspring of severely diabetic animals and related directly with increasing
fetal insulin levels (r = 0.77, P less than 0.005). Lipid analyses of fetal
lung membranes showed that reduction of phospholipid to protein ratios
occurred in the presence of maternal diabetes. Membrane
cholesterol-to-phospholipid ratios were also altered in the presence of
maternal diabetes. Significantly, increases in plasma membrane
microviscosity were noted in the membranes from diabetic offspring. The
data suggest that reduction of membrane fluidity is associated with
increases in fetal membrane insulin receptors in severely diabetic
pregnancies.
