Rabbit placental clearing-factor lipase and transfer to the foetus of fatty acids derived from triglycerides injected into the mother.

1. Lipase activity was measured in rabbit placental tissue fragments in late pregnancy. The activity in incubated tissue was greater with heparin (69%), reduced by NaCl (90%), but not affected by acetone or ether. 2. Pregnant rabbits (28-days gestation) were given triglyceride emulsions intravenously and the change in profile of fatty acids in the maternal and umbilical artery and vein plasma free fatty acid (FFA) measured. 3. Those fatty acids predominant in the emulsion were higher in concentration in the umbilical vein FFA than in the maternal plasma FFA and the venous-arterial difference was altered such that the placental transfer of FFA was enriched in a pattern corresponding to the profile of the fatty acids in the emulsion. 4. It is concluded that (i) the rabbit placenta shows considerable lipase activity and the lipase has the same characteristics as clearing-factor (lipoprotein) lipase, (ii) triglyceride infused into the mother is taken up by the placenta and hydrolysed, and (iii) the fatty acids so released pass through the placenta and are taken up by the foetus.