The interrelationships between circulating maternal esterified and non-esterified fatty acids in pregnant guinea pigs and their relative contributions to the fetal circulation.
The relative contributions of esterified and non-esterified fatty acids to placental lipid transfer were estimated in 7 pregnant guinea-pigs. The fetal side of the placenta was perfused in situ whilst a constant infusion of a mixture of [3H]triacylglycerol emulsion (Intralipid) and [14C]non-esterified fatty acid was given i.v. to the anaesthetised mother. Considerable interconversion of the lipid moieties circulating in the mother was observed. Metabolic turnover rates of triacylglycerol and non-esterified fatty acid were found to be 14.6 mmol/day and 55 mmol/day respectively. No intact triacylglycerol was found to cross the placenta from the mother. Relatively more [3H]non-esterified fatty acid than [14C]non-esterified fatty acid was found in the perfusion fluid when compared with simultaneous circulating maternal levels of these non-esterified fatty acids indicating hydrolysis and direct transfer of [3H]triacylglycerol within the placental tissue. This hydrolysis resulted in the transfer of approximately 0.2 mmol non-esterified fatty acid/day across each placenta at this gestational age (53 days). This is in contrast to the transfer of circulating maternal non-esterified fatty acids, these can be calculated to give a mother to fetus unidirectional transport value of 3.62 mmol/day/placenta, but the total maternal to fetal flux taking into account back transfer to the mother is 1.26 mmol/day/placenta. Results from simultaneous carotid artery and uterine vein samples showed that approximately 40% of the maternal arterial triacylglycerol is removed during a pass through the uterine bed, but the majority of the triacylglycerol re-emerges in the uterine vein as non-esterified fatty acids, and masks the uterine vein uptake of circulating maternal non-esterified fatty acid. The uterine vein non-esterified fatty acid concentration is highly dependent upon levels of circulating maternal triacylglycerols and apparent uterine bed production of non-esterified fatty acid occurs when maternal triacylglycerols are high relative to non-esterified fatty acids.
D000818:Animals; D002250:Carbon Radioisotopes; D002339:Carotid Arteries; D005227:Fatty Acids / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D006168:Guinea Pigs; D008657:Metabolic Clearance Rate; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D014280:Triglycerides / Q000097:blood; D014599:Uterus / Q000098:blood supply; D014680:Veins
D002250:Carbon Radioisotopes; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D014280:Triglycerides