SFD妊娠における胎盤のアミノ酸輸送機能とc-AMP systemに関する研究

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  • Studies on the Relation of Amino Acid Transport and c-AMP System in the Placenta of SFD Pregnancy
  • SFD ニンシン ニ オケル タイバン ノ アミノサン ユソウ キノウ ト c

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To elucidate the causes of SFD in cases with no maternal disease, such as toxemia, the author studied on the relation of placental cyclic AMP (cAMP) system and feto-maternal gradient of blood amino acid concentrations on the view-point of active transport of amino acids in the placenta.<br>The level of cAMP in the placenta was determined by the binding protein method, while adenyl cyclase activity was assayed by the modified Krishna's method and expressed as a conversion rate of 14C-cAMP formation under PG-E1 loading. The activity of placental phosphodiesterase was assayed by the method of Boudreau & Drummond, using theophylline as an inhibitor and imidazole as an activator. The maternal and fetal amino acid levels in human were determined by gas liquid chromatography. Studies were also made on the uptake of 14C-lysine in rat fetuses after loading of theophylline and dibutyryl cAMP on maternal rats.<br>The following results were obtained: (1) There was no difference of cAMP levels between the maternal and fetal side of the human placenta. (2) cAMP level in the placenta of normal pregnancy was significantly higher (20.24 p mole/mg protein) than that of SFD (6.18 p mole/mg protein). (3) The rate of placental adenyl cyclase activity in normal pregnancy was 1.97, while that in SFD was 1.26 being classifiable into three types from the figures of dose response curve by PG-E1 loading. On the contrary, the rate of placental phosphodiesterase activity was not significant among normal and SFD pregnancies. (4) Maternal amino acid levels in SFD pregnancy did not differ from that of normal, but the fetus/mother amino acid ratio (f/m ratio) in SFD pregnancy was lower than that of normal, showing a positive correlation (r=0.70) between the placental cAMP level and the f/m ratio. (5) 14C-lysine uptake in rat fetus was accelerated by theophylline loading on maternal rat but no by dibutyryl cAMP loading. In the same manner, cAMP levels in the placenta by theophylline loading on maternal rat increased significantly (1.23 p mole/mg wet weight) than that of non-loaded control (0.45 p mole/mg wet weight).<br>These results suggest that the weakening of amino acid transport activity in the placenta of SFD pregnancy with no maternal disease is ascribable to the decreased activity in the adenyl cyclase-cyclic AMP system

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