PHosphate metabolism and foetal growth in the rat. I. Net transfer of  31P and 32P phosphate from the maternal plasma to the normal placenta.
Net transfer of 31P and 32P inorganic phosphate form the maternal plasma to the rat chorio-allantoic placenta has been studied after intraperitoneal injection of [32P] ortho-phosphate in primigravid females at the 12th day or late stages of gestation. The concentration and label uptake per unit weight of placenta of the inorganic phosphate (Pi), organic-bound acid-soluble phosphate (POAS) and organic-bound acid-insoluble phosphate (POAIS) fractions are negatively correlated with increasing placental weight, whereas their specific activities are independent of placental weight. The amount and label uptake per whole placenta of the Pi, POAS and POAIS fractions are positively correlated with increasing placental weight. The placental concentrations of inorganic phosphate and calcium are positively related without, however, any marked accumulation of calcium. The growing placenta is thus shown to reduce progressively, on a unit weight basis, both the inorganic phosphate uptake from the maternal plasma and its further incorporation into organic-bound fractions. There is no evidence of a control by the foetal weight, acting per se, on these placental activities.
D000818:Animals; D005260:Female; D005333:Fetus / Q000502:physiology*; D007700:Kinetics; D008431:Maternal-Fetal Exchange; D009943:Organophosphorus Compounds / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains
D009943:Organophosphorus Compounds; D010710:Phosphates; D010761:Phosphorus Radioisotopes