Journal of Lipid Research, Vol. 9, 460-468, July 1968
Copyright © 1968 by Lipid Research, Inc.

Placental transport of free palmitic and linoleic acids in the guinea pig

Michael S. Hershfield and Andrew M. Nemeth

Anatomy Department, Medical School, University of Pennsylvania, Philadelphia, Pennsylvania 19104

Radioisotopic tracers were used to measure the unidirectional transfer rates of free fatty acids across the placenta of fed and fasted pregnant guinea pigs. Free ¹⁴C-labeled palmitic and linoleic acids (in serum) were injected simultaneously into a jugular vein of an anesthetized pregnant guinea pig. Serial samples of maternal blood were collected from a carotid artery; fetal blood was collected from the umbilical vein of an exposed fetus. Analysis of maternal and fetal plasma revealed that: (a) the half-lives of free palmitic and linoleic acid in maternal plasma are approximately 1.3 min and 0.7 min, both in fed animals with low plasma concentrations of these acids and in fasted animals with high concentrations; (b) free linoleic and palmitic acids cross the placenta from maternal to fetal plasma in a ratio of approximately 2.0, a value which appears not to change as the transfer rates of these acids from maternal to fetal plasma are increased by fasting the mother. It is suggested that the ratio in which free linoleic and palmitic acids cross the placenta from maternal to fetal plasma is determined by the ratio of the unbound free linoleic and palmitic acid concentrations in maternal plasma.

A comparison of several species indicates that a much greater proportion of fetal fatty acids comes from the mother in the guinea pig and rabbit than in the rat, the sheep, or man.

Supplementary key words placental transport • palmitic acid • linoleic acid • guinea pig • species differences • plasma FFA • half-life • turnover rate • blood sampling • exposed fetus

Submitted on May 23, 1967
Accepted on March 21, 1968

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