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Effect of maternal alcohol consumption on placental blood flow and fetal uptake of zinc, folate, and analogs of glucose and amino acid

University of British Columbia

The present study was undertaken to determine whether retarded fetal growth caused by maternal alcohol consumption prior to and during gestation is due to an interference with the transfer of nutrients from the maternal circulation into the fetus. Female Sprague-Dawley rats were either given 20 percent alcohol in drinking water and solid diet ad libitum (alcohol group), or were pair-fed to the alcohol group (pair-fed group), or were given water and solid diet ad libitum (ad libitum control group) for four weeks. They were then mated and the alcohol group was changed to 30 percent alcohol in water. During the third week of gestation maternal plasma levels of glucose, folic acid, and zinc were determined. On day 20 of gestation placental and fetal weights, the fetal uptake of zinc, folic acid, and non-metabolizable glucose and amino acid analogs, and the placental blood flow were determined. The fetal uptake of the nutrients studied was investigated by measuring fetal radioactivity 90 minutes after injecting the dams into the femoral vein with either ³H labeled folic acid and methyl (∝-D-U-¹⁴C gluco) pyranoside, or zinc-65, or 2-amino(1-¹⁴C) isobutyric acid. The radioactivity in the maternal plasma and liver 90 minutes after injection was also determined. Blood flow to the placentas as well as maternal cardiac output and renal blood flow were measured-fusing 15 micron diameter microspheres labeled with ⁵⁷Co. The osmolality of the maternal plasma and maternal muscle water content were determined in order to assess the degree of dehydration, as alcohol in water was offered as the sole source of fluids. No differences in litter size existed between alcohol and pair-fed or alcohol, and ad libitum control groups, however litter sizes of the ad libitum group were larger than those of the pair-fed group. The 20 day old fetuses were significantly smaller while the placentas were significantly larger in the alcohol group than in either the pair-fed or ad libitum controls. No differences were seen in maternal plasma levels of glucose, folic acid, or zinc among the three treatment groups. Cardiac output and blood flow to the kidneys did not differ among the three treatment groups. However blood flow to the placenta, whether expressed as mL/min/g placenta or as mL/min/ entire placenta or as % cardiac output was significantly reduced in the alcohol group compared with the pair-fed and ad libitum control groups. When expressed as mL/min/placenta differences in blood flow were also seen between pair-fed and ad libitum control groups. No significant differences were observed in the fetal uptake of zinc or analogs of glucose and amino acid between the three treatment groups. The folate taken up by the fetuses of the alcohol treated dams was significantly higher than for pair-fed but not ad libitum controls. No differences were observed in maternal plasma or liver concentrations of any of these compounds among the three groups 90 minutes after injection. Plasma osmolality was increased by approximately 7 percent in the alcohol group compared with pair-fed and ad libitum control groups. This indicates a moderate degree of dehydration. The present study demonstrates that the retarded growth of the fetuses exposed to alcohol in utero is not due to an impaired transfer of the nutrients tested from the maternal circulation to the fetus; nor is it due to lower maternal plasma levels of these nutrients. The significance of the reduced placental blood flow in the alcohol exposed rats on fetal growth and development is not clear. Thus the growth-retarding effect of maternal alcohol ingestion may still be due to a direct action of alcohol on the fetus.

Text

2010-03-26

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http://hdl.handle.net/2429/22507

Human Nutrition

University of British Columbia

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