CONCENTRATIONS OF AMINO-ACIDS IN PLASMA FROM 45-WEEK TO 47-WEEK GESTATION MARES AND FETUSES (EQUUS-CABALLUS)

Concentrations of 16 of 24 amino acids in plasma of foetuses were sign ificantly higher, while four of 24 were lower, than their concentratio n in maternal plasma. The higher foetal concentrations of amino acids in plasma are similar to other species, with some exceptions, and sugg est that equine placenta actively transports and concentrates amino ac ids into the umbilical circulation. Concentrations of nine of 24 amino acids were significantly lower in plasma from the umbilical artery co mpared to plasma from the umbilical vein, while no significant differe nces were present between maternal artery and vein plasma. The umbilic al venous-arterial difference in concentrations of amino acids in plas ma suggests the foetus extracts amino acids from the umbilical circula tion for catabolism or protein synthesis, as in other species.