The effect of chronic umbilical cord occlusion on mitochondrial protein abundance in the late gestation ovine fetus
MG Gnanalingham1, A Mostyn1, D Giussani2, T Stephenson1, ME Symonds1 & D Gardner1,2
Introduction: Umbilical cord occlusion (UO) sufficient to restrict fetal blood supply by 30 percent results in a range of fetal endocrine adaptations including increased fetal plasma cortisol. The extent to which this may promote premature maturation of fetal organs and tissues is not known. This study aimed to determine if UO results in premature maturation of mitochondria within fetal adipose tissue.
Methods: Nine ewes were entered into the study, which were all chronically instrumented with fetal vascular catheters. Five fetuses were then subjected to 3 days UO beginning at 125 days gestation by automated compression of the umbilical cord. At 137 plus/minus 2 days gestation all fetuses were euthanased, body weight measured and perirenal adipose tissue dissected and snap frozen in liquid nitrogen. Mitochondrial uncoupling protein (UCP)1, voltage-dependent anion channel (VDAC) and cytochrome c abundance were then determined by immunoblotting and results expressed as a percentage of a reference (ref) sample.
Results: There was no difference in body weights between groups (Control 2.85 plus/minus 0.23; UO 2.49 plus/minus 0.10 kg). UO resulted in enhanced abundance of UCP1 (Control 59 plus/minus 8; UO 97 plus/minus 8 percentage ref (P<0.05)) and VDAC (Control 85 plus/minus 11; UO 106 plus/minus 3 precentage ref (P=0.05)), but not cytochrome c abundance.
Conclusion: Chronic UO results in precocious maturation of adipose tissue. This may subsequently act to prevent the growth-restricted fetus from hypothermia at birth following cold exposure to the extrauterine environment.