Uptake and Metabolism of ¹⁴C-Palmitate by Fetal Rabbit Tissues

Abstract

The uptake and esterification of ¹⁴C-palmitate into lipid classes in placenta, fetal brown adipose tissue (BAT) and liver of rabbits were investigated in vitro. Fetal BAT showed a high rate of fatty acid uptake, 8.5 μmol·h^––¹ tissue·h^––1. From 5 min onwards, the majority of incorporated label was in the triglyceride fraction. The placenta and fetal liver also incorporated 1-[¹⁴C]-palmitate into both FFA and esterified lipid fractions, although at much lower rates than observed for BAT. In the liver, triglycerides, but in the placenta phospholipids, contained the majority of the label after 1 h incubation. BAT from both fetal and newborn rabbits released ¹⁴CO₂ and the production of ¹⁴CO₂ was greater in the presence of noradrenaline. The specific activity of the CO₂ was the same in stimulated and unstimulated tissue. It is concluded that BAT as well as the liver are important sites of free fatty acid removal from the fetal circulation. The potential for fatty acid oxidation is present in BAT of the 28-day rabbit fetus.

Ketone body metabolism during pregnancy in the rabbit

“…No anabolism has been observed in pregnant rabbits (Lebas, 1975 (Elphick et al, 1975 ;Elphick and Hull, 1977a,b ;Hudson and Hull, 1977 ;Stammers et al, 1983 Robinson and Williamson, 1980). The only data available have shown that blood ketone bodies remain very low throughout pregnancy in rabbits (Gilbert et al, 1984).…”

Distribution of Label in Maternal Plasma, Placenta, Fetal Plasma and Tissues after Injection of ¹⁴C-Palmitate into the Circulation of 21- and 28-Day-Pregnant Rabbits

“…In a previous paper (Hudson and Hull, 1977), it was found that the uptake of label per unit weight of fetal BAT in vitro was much greater than that of fetal liver and that the rate of fatty acid uptake by fetal BAT in vitro could account for up to 70% of the fat deposited in the tissue during the last 4 days of gestation. The difference between the results obtained in vitro and those in vivo can be attributed to the route of the fetal circulation, which enters the liver directly from the umbilical vein before passing into the rest of the circulation.…”

“…Thin-layer chromatography (TLC) of plasma samples was performed as described by Elphick et al (1975) and TLC of tissue samples as described by Hudson and Hull (1977). Recovery of radioactivity from TLC plates was: placenta 84 ± 2%, liver 96 ± 1% and BAT 94 ± 2% (mean ± SEM; n = 24).…”

Source of Fetal-Stored Lipids during Maternal Starvation in Rabbits

“…Fetal adipose tissue may have the capacity to regulate its own composi tion, as in the adult (20). If the pattern laid down reflects the composition of a fatty acid pool that exchanges with adipose tissue triglyc eride fatty acids and plasma FFA (12), then the possibility of a fatty acid accumulating in fetal adipose tissue to an extent greater than its relative abundance in fetal plasma FFA might be less likely.…”