Down-regulation of albumin synthesis in the rat by human recombinant interleukin-1 beta or turpentine and the response to nutrients.

BACKGROUND Inflammatory stimuli and provision of nutrients are important factors regulating both total liver protein synthesis and albumin synthesis. METHODS The influence of interleukin-1 beta or turpentine injection and a 2-hour infusion of a hypocaloric mixture of glucose and amino acids on the synthesis of total liver protein and albumin was investigated in rats. Total liver protein synthesis was measured by an i.v. flooding dose of L-[2,6(3)H]phenylalanine and albumin synthesis was determined from the labeling of immunoprecipitated albumin and expressed both as a fraction of total liver protein synthesis and as an absolute rate. RESULTS Interleukin-1 beta or turpentine injection stimulated total liver protein synthesis compared with controls, whereas albumin synthesis, both as a fraction of total liver protein synthesis and as an absolute synthesis rate, decreased. In control animals, the 2-hour i.v. infusion with glucose and amino acids resulted in a significant increase of total liver protein synthesis. Albumin synthesis as a fraction of total liver protein synthesis was not altered, but increased when expressed as an absolute rate in control animals. However, interleukin-1 beta or turpentine injection abolished this response of albumin synthesis to nutrient supply. CONCLUSIONS Total liver protein synthesis increases under inflammatory conditions and remains responsive to nutrient supply. In contrast, albumin synthesis decreases under the same conditions and does not seem to be responsive to short-term i.v. nutrients.