Aberrant tyrosine transport across the cell membrane in patients with schizophrenia

There is evidence that patients with schizophrenia exhibit abnormalities, not only in the brain but also in peripheral organs. An abnormal cell membrane composition has been suggested to be a common denominator, supported by findings of alterations in membrane phospholipid levels. In a previous study, the transport of amino acids across the plasma membrane was investigated with fibroblasts from patients with schizophrenia and controls. An isolated decrease in the maximal transport capacity (V(max)) of tyrosine was observed in the cells from patients. In this context, tyrosine transport across the fibroblast membrane was investigated in patients with schizophrenia and healthy control subjects.

Skin fibroblasts were obtained from 36 patients with schizophrenia (15 first episode and 21 chronic) and 10 healthy controls. Tyrosine transport across the cell membrane was studied in cultivated fibroblasts. The V(max) and the affinity of the tyrosine binding sites (K(m)) were determined.

Significantly lower V(max) (F(1,41) = 12.80; P =.001; effect size = 1.36) and K(m) (F(1,41) = 24.85; P<.001; effect size = 1.00) were observed in fibroblasts from the patients. The findings were present in both neuroleptic-naive patients with their first episode and patients with chronic schizophrenia.

The lower V(max) and K(m) are compatible with a cell membrane disturbance and support the view of schizophrenia as a systemic disorder. The decreased V(max) and K(m) observed in cells from schizophrenic patients probably reflect a genetic trait, as the changes were transmitted through several cell generations of cultured fibroblast.