Sandwich enzyme immunoassay of dopamine-β-hydroxylase in cerebrospinal fluid from control and parkinsonian patients

Abstract

A sandwich enzyme immunoassay (EIA) was established by using purified human serum dopamine-β-hydroxylase (DBH) as a standard protein and a monospecific polyclonal antibody raised against human DBH purified from human pheochromocytoma. The EIA was applied to measuring DBH levels in human CSF from Parkinsonian patients and control patients devoid of neurological diseases. The control group had DBH content of 21.1 ± 3.1 ng/ml CSF and DBH activity of 24.0 ± 3.7 μ U/ml CSF, and Parkinsonian group 3.3 μ 0.7 ng/ml CSF (16% of control) and 4.6 ± 0.7 μU/ml CSF (19% of control) (mean ± SEM). Thus, both DBH content and DBH activity in CSF were reduced in Parkinsonian patients to less than 20% of the control values ( P $ ̌ 0.005 ). However, the specific activity (units of enzyme activity/mg of DBH protein) in CSF of Parkinsonian patients was similar to that of control patients. These results suggest that the reduced DBH activity in CSF from Parkinsonian patients is caused by a reduction in DBH protein content, and is not due to production of an inactive form of DBH, for example, by combining with endogenous inhibitor(s). These data support our previous findings that DBH activities in the Parkinsonian brain and CSF are decreased.