Selective changes to phosphatidylcholine and phosphatidylethanolamine molecular species in the developing fetal guinea pig liver and plasma.

The molecular species composition of membrane phospholipids influences the activities of integral proteins and cell signalling pathways. We determined the effect of increasing gestational age on fetal guinea pig liver phosphatidylcholine (PC) and phosphatidylethanolamine (PE), and plasma PC molecular species composition. The livers were collected from fetuses (n = 5/time point) at 5 day intervals between 40 and 65 days of gestation, and at term (68 days). Hepatic PC and PE molecular species composition was determined by electrospray ionisation mass spectrometry. An increasing gestational age was accompanied by selective changes in individual molecular species. The proportion of the sn-1 18:0 species increased relative to the sn-1 16:0 species in liver PC, but not PE, with an increasing gestational age. 1-O-alkyl-2-acyl PC species concentrations decreased significantly between 40 and 45 days of gestation (40%), and 65 and 68 days (54%). Total 1-O-alkenyl-2-acyl PE species concentration increased between days 60 and 65, due to a rise in 1-O-16:0 alkyl/20:4 content, and then decreased until term. Between day 40 and term, PC and PE sn-2 18:2n-6 species concentrations increased 3-fold. PC16:0/18:2 increased gradually throughout gestation, while PC18:0/18:2 content only increased after day 65. The overall increase in PE18:2n-6 content was due to PE18:0/18:2 alone. The composition of plasma PC essentially reflected hepatic PC. Overall, these data suggest differential regulation of hepatic PC and PE molecular species composition during development which is essentially independent of the maternal fatty acid supply.