DECREASE IN RED-BLOOD-CELL L-TRYPTOPHAN UPTAKE IN SCHIZOPHRENIC-PATIENTS - POSSIBLE LINK WITH LOSS OF IMPULSE CONTROL

1. Kinetic parameters of erythrocyte L-tryptophan (TRP) uptake (Vmax, maximal velocity and Km, Michaelis constant) were determined in 19 neu roleptic-free schizophrenic patients and in 19 healthy volunteers. Bot h Vmax and Km values were significantly lower in schizophrenic patient s than in controls. 2. Mean Vmax value was found to be lower in patien ts who had attempted suicide than in patients who had not. No differen ce was observed when patients were subdivided on the basis of the viol ence of suicide attempts. 3. A significant negative correlation was ob served between Vmax and scores on the loss of impulse control item as assessed on the PANS scale. 4. Decrease in red blood cell L-TRP uptake reflects a disturbance in the peripheral metabolism of TRP that may r esult in a deficiency of the plasma L-TRP availability on which the ce ntral serotonin (5HT) synthesis closely depends. 5. In addition, the r esults suggest that the alteration in RBC L-TRP uptake is associated w ith loss of impulse control in schizophrenic patients.