Radioimmunoassay of beta-endorphin in ventricular and lumbar cerebrospinal fluid.

We describe a sensitive beta-endorphin (beta-EP) radioimmunoassay specific for beta-EP 1-31 applied to human ventricular and lumbar cerebrospinal fluid (CSF). Specificity was documented by reversed-phase HPLC of CSF pools. Simultaneous ventricular and lumbar CSF samples from 13 patients suspected of having normal-pressure hydrocephalus showed median beta-EP values of 2.2 (range 1.7-4.0) and 4.8 (2.8-14.6) pmol/L, respectively. Ventricular and lumbar beta-EP concentrations were positively correlated (Spearman r = 0.72, P = 0.013). The beta-EP rostral-caudal gradient was closely related to the CSF protein gradient. HPLC profiles of beta-EP immunoreactivity were similar in ventricular and lumbar CSF with both C- and N-terminal antisera. beta-EP concentrations did not vary in the first 12 mL of lumbar CSF, tapped in 3-mL portions [F(3,32) = 0.42, P = 0.74]. The beta-EP concentration in lumbar CSF from 15 children in remission from acute leukemia [23.4 (15.0-27.1) pmol/L] was higher than in 54 healthy adults [11.7 (10.9-13.3) pmol/L; P less than 0.01]. There was no effect of sex or age on CSF beta-EP in adults. beta-EP in lumbar human CSF may indicate di- and mesencephalic beta-EP neuronal activity.