Abnormalities in 14CO2 Production from DL-3,4-Dihydrophenylalanine-Carboxyl-14C By Red Blood Cell in Schizophrenia

Decarboxylation of Radioactive DOPA by Erythrocytes in Schizophrenia

Ngô Mạnh Trần, Marcel Laplante and Etienne LeBel

University Medical Center, Sherbrooke, Quebec, Canada

A combined vibrating reed electrometer-ionization chamber method has been used for an instantaneous and continuous measurement of 14CO2 production from DL-3,4-dihydroxyphenylalanine-carboxyl-14C (dopa) by mature red bood cells of seven (7) normal subjects, four (4) schizophrenics “ in remission” (patients had hallucinations or thought disorders or both at some time in the past but not at time of the strudy) and five (5) schizophrenics with active hallucinations and thought disorders. Such a method allowed an immediate determination of the rate and amount of 14CO2 excreted by RBC, after incubation with a 14C-labeled biochemical in Gey’s balanced salt solution gassed with 5% CO2, 95% O2.

In normal volunteers approximately 0.36%/100 millions RBC of 14C incubated as dopa-carboxyl-14C appears as 14CO2 within 180 minutes. This result suggests that the decarboxylase activity involved in the oxidation of dopa must occur in normal and mature human RBC.

No significant (p≥ 0.05) in 14CO2 production from 14C-labeled dopa by RBC was observed in schizophrenic patients “in remission”.

A significant increase (p≤ 0.05) was, however, noted in 14CO2 production in the small group of schizophrenics with hallucinations and severe thought disorders.

This latter result may be due to either an increased dopa decarboxylation activity in RBC or an increased physical transport of DL-dopa across the cell membrane, or both.

The second possibility was supported by our recent finding which demonstrated an increased incorporation rate of dopa into RBC of schizophrenics with hallucinations or severe thought disorders or both in an in vitro study using RBC of normal volunteers and patients incubated with DL-dopa-2-14C in basal medium of Eagle (BME). A drug effect (i.e., chlorpromazine) was excluded as the source of the difference of 14CO2 production of dopa into RBC. This was shown in another study using RBC incubated with Dopa-2-14C in the presence or absence of chlorpromazine.

These observed abnormalities in the decarboxylation of dopa by RBC of these patients may offer the most direct evidence of data for the occurrence of abnormal dopa metabolism in schizophrenia.

References:

1)      Journal of Nuclear Medicine 10: 664, 1971

2)      British Journal of Psychiatry (England), 118 (545): 465-466, 1971

Decarboxylation of Radioactive DOPA by Erythrocytes in Schizophrenia

NGO TRAN, MARCEL LAPLANTE, and ETIENNE LEBEL

Medicine..Schizophrenia

Medicine..Hallucinations

Chemistry..Decarboxylation

Physiology..Humans

The British Journal of Psychiatry (1971) 118: 465-466.
© 1971 The Royal College of Psychiatrists. This article can be searched in Google Web site.

Chú thích: Ngày nay, chúng ta thấy nhiều nghiên cứu về vai trò của DOPA liên hệ bệnh phân liệt tâm thần.

Thí dụ:

1/ bài của các tác giả Inanaga K., Inoue K., Tachibana H., Oshima M., Kotorii T nói về tác dụng của L-dopa trong bệnh tâm thần phân liệt:

Effect of L-dopa in schizophrenia, Folia Psychiatr Neurol Japan, 26 (2): 145-57, 2003.

2/ Tác dụng lâm sàng của L-dopa vào bệnh tâm thần phân liệt, Clinical effect of L-dopa on schizophrenia của các tác giả Ogura C., Kishismotoa A., Nakao T. trong Curr Ther Rese Clin Exp, 20: 308-18, 1976.

3/ Trị liệu phụ dùng Levodopa cho bệnh tâm thần phân liệt có hiệu quả thêm cho bệnh nhân: A meta-analysis of the response to chronic l-dopa in patients with schizophrenia: therapeutic and heuristic implications", Psychopharmacology, 171: 4: 365-74, 2004.

4/ Nghiên cứu cấu trúc di thể dopa decarboxylase ảnh hưởng tuổi tác khi phát hiện bệnh tâm thần phân liệt: Dopa decarboxylase genotypes may influence age at onset of schizophrenia. Molecular Psychiatry, 6: 712-717, 2001.

5/ Tăng cao tác dụng Dopa decarboxylase trong não bệnh nhân bị bệnh loạn tâm thần: Elevated dopa decarboxylase activity in living brain of patients with psychosis, Proceedings of the National Academy of Sciences, 91: 11651-11654, 1994.

6/ Nhiều nghiên cứu liên hệ giữa L-dopa và bệnh tâm thần phân liệt có thể search trong các web sites như Google, Yahoo.

Bs Trần Mạnh Ngô

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