Specific binding of 3H-spiperone to peripheral blood cells: relevance for the interpretation of binding studies in psychiatric disorders.
1. There is an ongoing discussion regarding the elevated binding of 3H-spiperone to lymphocytes of schizophrenic patients. Several authors described an atypical binding pattern with a saturable high-affinity and a nonsaturable binding site both displaceable by (+)-butaclamol. Recent findings are still controversial (Fartacek et al., 1997; Wodarz et al., 1996), possibly due to methodological differences. The authors investigated 3H-spiperone binding to different peripheral blood cells including B- and T-lymphoblastoids. 2. B-lymphocytes (KD = 0.081 nM; Bmax = 0.46 x 10(-15) mol/10(6) cells) and macrophages (KD = 0.1-1 nM, Bmax = 2.44 x 10(-15) mol/10(6) cells) are characterized by a minor but saturable binding of 3H-spiperone in a concentration range between 0.5 and 1 nM. Above 1 nM, only non-saturable binding was measurable. Interestingly, Epstein-Barr virus (EBV) transformed lymphoblastoids (KD = 0.13 nM) have nearly the same affinity for 3H-spiperone as native B-cells, but an increased number of binding sites (Bmax = 1.76 x 10(-15) mol/10(6) cells). 3. Membranes from B-lymphoblastoids displayed a saturable binding in a concentration between 0 and 1.8 nM of 3H-spiperone (KD = 0.5 nM and Bmax = 1.72 x 10(-15) mol/mg protein). Extraction with 1% digitonin resulted in a similar binding characteristic (KD = 0.17 nM and Bmax = 1.97 x 10(-15) mol/mg protein). 4. T-cells, granulocytes and MOLT-3-cells did not show is a saturable binding even not at high concentrations of 3H-spiperone. 5. The pharmacological profile of the high-affinity 3H-spiperone binding site is clearly different from the dopamine D2 and D4, serotonin 5-HT2 histamine H1 and noradrenergic alpha1 and alpha2 receptor, respectively. 6. In summary, the results suggest that spiperone binding studies to enriched lymphocytes of psychiatric patients should be interpreted cautiously. Variable amounts of leucocytes might result in a higher proportion of nonsaturable, butaclamol displaceable spiperone binding with relevance for the calculation of KD and Bmax of the saturable high-affinity site. Interestingly, homogenous B-lymphoblastoid cell lines have the same binding characteristics as native B-lymphocytes and therefore should be recommended for characterization of 3H-spiperone binding sites.
Henning
U
U
Department of Psychiatry, University of Düsseldorf, Germany. KN27120@mail.lvr.de
Krieger
K
K
Klimke
A
A
D001402:B-Lymphocytes / Q000502:physiology*; D001665:Binding Sites; D015415:Biomarkers / Q000032:analysis; D018491:Dopamine Agonists / Q000494:pharmacology*; D006801:Humans; D008264:Macrophages / Q000502:physiology*; D001523:Mental Disorders / Q000503:physiopathology*; D013134:Spiperone / Q000494:pharmacology*; D014316:Tritium
D015415:Biomarkers; D018491:Dopamine Agonists; D014316:Tritium; D013134:Spiperone