Hepatic phospholipid molecular species in the guinea pig. Adaptations to pregnancy.

Incorporation of polyunsaturated fatty acids (PUFA), particularly 22:6n-3, into fetal brain at specific gestational ages is critical for development of normal brain function. We have studied adaptations to maternal liver phospholipid molecular species compositions that may be related to the supply of PUFA to fetal brain. The increment of 22:6n-3 in brain phosphatidylethanolamine (PE) was maximal at day 25 to day 35 of gestation, consistent with early prenatal development of guinea pig brain. At the same gestational ages, there was a transient increase in maternal liver concentration of 16:0/22:6 phosphatidylcholine (PC), which preceded the progressive increase in total PC concentration toward term (day 68). This effect was specific for the sn-1 16:0 species, as there was no significant increase in 18:0/22:6 PC concentration. These results are consistent with a specific role for 16:0/22:6 PC in the directed supply of 22:6n-3 from maternal liver to the fetus. Concentrations of all PE species in maternal liver decreased at day 25 and day 35 of gestation. The gradual accumulation of 22:6n-3 in fetal liver throughout gestation did not correlate with the pattern of acquisition of 22:6n-3 into fetal brain PE. Maternal plasma PC and cholesterol concentrations decreased dramatically by day 25 of gestation, and remained low until term. This hypolipidemia of pregnancy in the guinea pig may be due to increased lipase-mediated turnover of plasma lipoproteins and contrasts strongly with the well-characterized hyperlipidemia in human and rat gestation.