The relationship between placental protein synthesis and transfer of amino acids

Abstract

The relationship between placental protein synthesis and transfer of amino acids from mother to fetus was studied in the guinea pig, by using [U-14C]-lysine, -leucine, -glycine, -aspartate and -.alpha.-aminoisobutyrate. The uptake of label by protein was 12-16% of total label transformed. Cycloheximide inhibited incorporation of all naturally occurring amino acids into protein by 81-96% and transfer by 62-75%; the concentration of label in the free pool was increased for each. These findings were confirmed when specific radioactivity measurements were made with L-[U-14C]lysine. The transfer of the nonprotein amino acid .alpha.-aminoisobutyrate was not significantly decreased by cycloheximide. A model, linking protein synthesis to the generation of a transfer pool of amino acids, is proposed whereby inhibition of protein synthesis decreases the amount of amino acid available for transfer.