PREGNANCY-ASSOCIATED ADAPTATIONS TO HEPATIC PHOSPHATIDYLCHOLINE BIOSYNTHESIS IN THE GUINEA-PIG

Pregnancy is associated with increased phosphatidylcholine (PC) 16:0/2 2:6 and PC16:0/20:4 concentrations in rat liver and plasma, guinea-pig liver, and in plasma in women. These changes may be related to supply of polyunsaturated fatty acids (PUFA) to the fetus. For the rat, thes e adaptations to hepatic PC composition are regulated by modifications to synthesis de novo from choline. However, it is not known whether t hese adaptations are applicable to other species. Consequently, we hav e determined biochemical mechanisms for regulation of hepatic PC synth esis in the pregnant guinea pig. The PUFA content of guinea-pig liver PC synthesised de novo did not change significantly during pregnancy. [Methyl-C-14]methionine incorporation into PC in vivo, however, showed increased PC16:0/22:6 and PC16:0/20:4 contents. [Methyl-C-14]methioni ne incorporation into PC over 6 hr in vivo increased during early preg nancy, while PC synthesis de novo did not change. In contrast to the r at, modulation of PE N-methylation is a primary mechanism for regulati ng the PUFA content of hepatic PC in the pregnant guinea-pig. The use of distinct metabolic strategies to achieve comparable pregnancy-assoc iated adaptations to hepatic PC composition between these animal speci es suggests both evolutionary convergence and a fundamental the role f or PC16:0/22:6 and PC16:0/20:4 in PUFA metabolism during gestation. (C ) 1998 Elsevier Science Inc.