Fetal supply of amino acids and amino nitrogen after maternal infusion of amino acids in pregnant sheep.

Abstract

The objective of the study was to determine whether a prolonged maternal infusion of amino acids would increase the umbilical uptake of amino acids and uteroplacental ammonia production. Six pregnant sheep (134.5 2.3 days after conception) were infused for 12 hours overnight with an amino acid solution. Uterine and umbilical blood flows were measured with the ethanol steady-state diffusion technique before (control) and during (experimental) infusion. Plasma amino acid and whole-blood ammonia concentrations were measured. After infusion, despite an increase in maternal arterial amino acid concentration, umbilical uptakes increased significantly only for branched-chain amino acids. Fetal ammonia concentrations and uteroplacental ammonia production increased moderately. Fetal nitrogen supply did not increase. Uterine nitrogen uptake represented 36% of the maternal nitrogen intake in the control period and 14% in the experimental period. Prolonged maternal infusion of an amino acid solution was a relatively ineffective method of increasing fetal amino acid supply.