Characterization of N-terminal fragment of proopiomelanocortin in cerebrospinal fluid

Abstract

The molecular forms of the N-terminal fragment (hNT) of proopiomelanocortin were studied in cerebrospinal fluid (CSF) from normal subjects, methadone-addicted patients, patients with hydrocephalus, and a patient with Nelson's syndrome. The peptides were characterized by molecular sieving and Concanavalin A-Sepharose chromatography. Immunoreactivity was detected using antibodies directed against the N- and C-terminal portions of the hNT (hNT and gamma 3MSH antibodies, respectively). The mean immunoreactive hNT (IR-hNT) levels in samples of CSF from normal subjects, patients with hydrocephalus, methadone addicts, and the patient with Nelson's syndrome were 410 +/- 158 (+/- SE), 435 +/- 137, 328 +/- 183, and 85,700 pg/mL, respectively. Molecular sieving chromatography revealed one predominant species of IR-hNT and/or gamma 3MSH which coeluted with the authentic hNT-(1-76) marker. However, 10-16% of the total immunoreactivity eluted close to the void volume. No significant differences in the elution profiles were found among these groups. Most (61-69%) of the IR-hNT bound to Concanavalin A, and the elution patterns of samples from this column were similar to that of purified hNT-(1-76). These results support the view that the major molecular form of hNT in CSF is NT-(1-76) as it is in the pituitary gland.