抄録
In our previous report, we presumed that there is a depressed transport of amino acids in the small-for-date (SFD) placenta. To substantiate this presumption, we conducted in vitro experiments with normal and SFD placental slices and compared their uptakes of amino acids, serine and lysine. Activity of Na-K ATPase in the trophoblastic membrane was also studied. (1) In both normal and SFD placentas, uptakes of amino acids were about two to three times as great for neutral amino acid serine as for basic amino acid lysine. (2) In the SFD placenta, amino acid uptake became significantly slower than in the normal after 30 min of incubation. After 90 min the uptake was lower than the normal by some 32% for serine and 42% for lysine. (3) Serine uptake began to be interrupted by the addition of 10-3M ouabain at 30min, and showed about 31% decrease at 90min, revealing an amino acid uptake pattern similar to that of the SFD placenta. But lysine uptake was not noticeably affected by ouabain. (4) As for the release of intracellular amino acids into the incubation medium, no differences could be observed either between serine and lysine or between the normal and the SFD placenta. (5) Activity of transport ATPase of the isolated trophoblastic membrane was lower in the SFD than in the normal placenta. The findings tend to corroborate the suggestion that the low f/m ratio of amino acids in SFD pregnancy accounts for a decreased placental transport of amino acids corresponding with depression in the activity of its major promotor
