[The regulation of serum albumin in physiological and pathological conditions (author's transl)]

Abstract

12 g of albumin are synthesized daily by the bound polyribosomes of all human liver cells together, corresponding to 10% of the intravascular albumin mass. The cell is producing a precursor albumin. During secretion albumin is liberated by splitting of a small peptide. Only 40% of the total body albumin is located intravascularly. 12g of albumin are degraded or excreted daily, 30% of it by the liver, the kidneys and the gastrointestinal tract. The main site of albumin catabolism is unknown. Albumin with a half-life of about 20 days is degraded at a constant fractional catabolic rate. The absolute rate of degradation varies depending on the plasma content. This mechanism allows an effective regulation of the serum albumin level. The fractional catabolic rate, however, is not completely fixed. It is slowly reduced if the serum albumin content is markedly reduced as in protein deficiency, the blind loop syndrome, cirrhosis, nephrosis, and diseases of the gastrointestinal tract. Infusion of albumin increases the fractional catabolic rate slowly. This must be taken in consideration substitution albumin in chronic diseases. The shift from the extravascular to the intravascular compartment is a short-term regulatory mechanism. The regulation of synthesis and degradation are independent from each other. The molecular mechanism of regulation of synthesis and degradation are unknown, partially due to inadequate methods.