TISSUE AMINO ACID RESPONSES TO PARENTERAL NUTRITION

Abstract

We have previously described significant differences in plasma amino acids, bile flow and biliary bile acid output between animals infused either glucose or glucose+amino acids. The present study was undertaken to determine liver, bile and brain amino acid responses to the infusion of these various nutrients. Adult male Sprague-Dawley rats (225-325g) were cannulated via the jugular vein and infused with either glucose (GLU) or glucose+amino acids (TPN) or were chow-fed (CHOW). After 5 days of the respective regimens, bile was collected for 4h, animals were killed and brain and liver obtained. The GLU animals received 164 (SD 7) kcal/kg/d, whereas TPN animals received 9.4 (0.5)g AA and 154 (8) kcal/kg/d. Both GLU and TPN animals lost weight and CHOW animals gained weight. In general, the tissue amino acid patterns were similar to those in plasma; most individual amino acids were different among groups in liver and bile whereas only threonine, valine and isoleucine concentrations were different among the groups in the brain. Essential to non-essential amino acid ratios (markers of protein nutritional status) were: 0.59, 0.51 and 0.36 in the plasmas; 0.18, 0.11 and 0.09 in the livers; and 0.29, 0.29 and 0.22 in the bile of TPN, CHOW and GLU animals respectively. The branch chain amino acids are actively accumulated in the liver from the plasma and then appear to be passively tranported down a concentration gradient into the bile. Thus, the amino acid responses to these nutritional manipulations indicate that tissues (primarily the liver) may be susceptible to the trophic and toxic effects of amino acids.