PORTAL-DRAINED VISCERA AND HEPATIC FLUXES OF BRANCHED-CHAIN AMINO-ACIDS DO NOT ACCOUNT FOR DIFFERENCES IN CIRCULATING BRANCHED-CHAIN AMINO-ACIDS IN RATS FED ARGININE-DEFICIENT DIETS

Concentrations and fluxes of amino acids across the portal-drained vis cera (PDV) and liver were assessed in rats fed a meal of one of three arginine-deficient diets containing either alanine or the arginine pre cursors, ornithine or citrulline. A previous report included findings of seven arginine-related amino acids and indicated that only the citr ulline-containing diet protected blood arginine concentrations. In the present report we extend these findings and note that the concentrati ons and fluxes of the non-arginine-related amino acids showed remarkab le consistency across diet groups. However, total branched-chain amino acid (BCAA) concentrations of arterial blood were higher in rats fed the -Arg/+Ala and the -Arg/+Orn diets than in rats fed the control (+A rg) diet. The elevated BCAA correlated with higher circulating concent rations of other essential amino acids but were inversely correlated w ith arginine concentrations. PDV and hepatic fluxes of BCAA were not d ifferent across diet groups, indicating that amino acid absorption and hepatic utilization of BCAA were generally comparable across diet gro ups. Hepatic concentrations of 14 of 22 measured amino acids, includin g total BCAA, were correlated with their arterial concentrations. The circulating concentrations and net PDV and hepatic fluxes of rats feci the control diet were comparable to our previous observations in fed rats and illustrate the role of the liver in utilization of diet-deriv ed essential amino acids.