Changes in the concentration of free choline and cephalin-N-methyltransferase activity of the rat material and foetal liver and placeta during gestation and of the maternal and neonatal liver in the early postpartum period.

Abstract

Summary 1. The concentration of free choline and cephalin-N-methyltransferase activity were determined for the rat maternal and foetal liver and placenta during gestation, and for the maternal and neonatal liver during the early postpartum period. Choline was determined by bioassay and the enzyme activity by using S-adenosyl-L-(14C-methyl)-methionine. 2. There was a significant and progressive fall in the choline concentration (nmol/g tissue) of the maternal liver from the control value of 130 (s.e.m. = 9) to 93 (s.e.m. = 9) after about 11 days gestation and to 38 (s.e.m. = 1) from about 17 days gestation to term; however, there was a gradual rise in the corresponding enzyme activity (counts/min) from a mean value of 561, s.e.m. = 7, (control to 618 (s.e.m. = 14) and then to 693 (s.e.m. = 19). 3. At 1 day postpartum both the choline concentration (166, s.e.m. = 9) and the enzyme activity (738, s.e.m. = 45) of the maternal liver increased appreciably and reached a peak before gradually declining to the control value at about 3 and 7 days postpartum, respectively. 4. The hepatic choline concentration of the foetus at 20 to 22 days gestation (135, s.e.m. = 6) was similar to adult (control) levels, although its cephalin-N-methyltransferase activity was very low (about 20% of control). 5. The choline concentration of the neonatal liver increased to 220 (s.e.m. = 21) and then to 272 (s.e.m. = 17) at 1 day and at about 3 days postpartum followed by a decline to the adult (control) value at about 7 days postpartum. The enzyme activity, however, increased continuously to attain adult levels at about 10 days postpartum. 6. The placental choline concentration was about three to four-fold greater than that of the control liver. The values obtained were 370, s.e.m. = 27 (14 to 16 days gestation), 426, s.e.m. = 27 (17 to 19 days gestation) and 442, s.e.m. = 18 at term. However, the cephaline-N-methyltransferase activity was undetectable in the placentae. 7. The choline concentration of the maternal plasma(5.3, s.e.m. = 0.7) remained essentially constant throughout gestation and in the early postpartum period. 8. The results strongly suggest that, during pregnancy, the rat maternal liver supplies free choline to the placenta and foetal liver and that the demand for maternal liver choline probably exceeds the supply available.