A Comparative Characteristic of Amino Acid Composition and Activity of Amino Acid Metabolism Enzymes in Hemochorial Placenta of Various Animal Species and Humans

The amino acid composition and activity of the enzymes of placental amino acid metabolism were studied in guinea pigs ( Cavia porcellus ) and rhesus macaques ( Macaca mulatta ) which have a hemochorial type of placenta, similar to that in humans. The study also included women with uncomplicated pregnancy and delivery at full term (39–40 weeks). It was established that the fetal (chorionic) part of the placenta is characterized by the highest level of free and bound amino acids and maximum activity of enzymes related to amino acid metabolism (aminotransferases, deaminases, amino synthetases) in all tissues studied. A high level of dicarboxylic amino acids and glutamine is also common to the placenta of guinea pigs, monkeys and humans. Along with common traits, placental amino acid metabolism in different animal species and humans reveal some differences depending on the evolutionary features of the organ’s development and the specificity of the existing maternal-fetal relationships. Interspecies differences between the analogous parts of the placenta concern individual amino acids, the level of most of which in the placenta of rodents exceeds the same indices in primates. The relevant differences between human and apish placentas are less pronounced. The guinea pig placenta is different from those in humans and monkeys in the mode of non-covalent binding of amino acids to biopolymers, which modifies the state of the acceptor protein groups. Analogous afterbirth tissues in different animal species and humans differ in the activity of the enzymes of amino acid metabolism. There is a close correlation between the level of free amino acids and the indices of enzyme activity, indicating their important role in the formation of the placental amino acid pool.