LOWER SERUM L-TRYPTOPHAN AVAILABILITY IN DEPRESSION AS A MARKER OF A MORE GENERALIZED DISORDER IN PROTEIN-METABOLISM

Recently, it has been reported that major and melancholic depression a re accompanied by a lower availability of total L-tryptophan (L-TRP) t o the brain and by significant changes in electrophoretically separate d protein fractions, such as albumin and alpha(2)-globulin. The aim of this study was to examine the relationships between serum L-TRP avail ability and total serum protein, albumin, and alpha(2)-globulin in 42 depressed and 24 normal subjects. In depressed and normal subjects, al one and together, there were significant and positive correlations bet ween serum L-TRP and total serum protein or albumin concentrations. In the depressed subjects, but not in normal controls, there were signif icant inverse relationships between the L-TRP/competing amino acid rat io and alpha(2)-globulin fraction. Serum L-TRP and albumin were signif icantly lower in melancholic subjects than in normal and minor depress ed subjects. Depressed subjects had a significantly lower L-TRP-compet ing amino acid ratio and significantly higher serum alpha(2)-globulin than normal controls. Total serum protein was significantly lower in m ajor depressed is related to lower serum albumin and to increased alph a(2)-globulin fraction, which are both hallmarks of the acute phase re sponse in depression. The results further corroborate the hypothesis t hat lowered L-TRP availability in depression is related to the acute p hase response in that illness.