The Distribution and Metabolism of Carbon-Labeled Urea in Pregnant Primates*

Transfer of radioactive water, urea and glycine between maternal and foetal body fluids in rabbits and pigs

“…In every instance of injection of radioactive material into the maternal circulation, the specific activity in the foetal blood rose, at least temporarily, to a higher level than that in the maternal blood. This phenomenon was observed also by Hutchinson et al (1962) in pregnant rhesus monkeys after an injection of 14C-urea. There appears to be a temporary accumulation of the isotope in the foetal blood, followed by its dispersion through the remaining foetal tissue.…”

“…MARGARET W. STANIER of course imply the existence of a net transport of urea in this direction. The observations in this paper in no way conflict with those on rhesus monkeys made by Hutchinson et al (1962), who recorded that it was not possible to demonstrate net transfer of urea from foetus to mother. From the pig's allantoic sac, tritium-labelled water showed a slower but moderate movement, at least at 67 and 74 days gestation, at which stage the absolute volume of allantoic fluid is maximal or decreasing.…”

Fetal insulin and growth hormone metabolism in the subhuman primate

“…The experimental technique involved cannulation of, and blood sampling from, interplacental fetal vessels in the pregnant monkey (Macaca mulatta). The use of this animal as a model for placental transfer and fetal metabolic studies has been previously described (10)(11)(12)(13). In an attempt to define any modifying influence of the placenta on fetal plasma responses, the bidirectional placental transfer of radioisotopically labeled insulin, and the neonatal plasma responses to the same stimuli were examined.…”

Integrated profiling of metabolites and trace elements reveals a multifaceted malnutrition in pregnant women from a region with a high prevalence of congenital malformations

“…The enhanced amino acid oxidation could lead to an increased urea synthesis and urea nitrogen level in maternal blood and urine ( Table 2). As urea concentration in maternal and fetal blood is nearly same through the exchange of urea in both of the circulations (Hutchinson et al 1962), an unusual accumulation of maternal urea cycle metabolites due to pathophysiological change, may lead to an increase of these metabolites in fetal blood. Unfortunately, the significant elevation of urea excretion in a fetus causes chronic neurotoxicity to the fetus (Matsuoka and Igisu 1993).…”