Evidence for a novel pituitary protein (7B2) in human brain, cerebrospinal fluid and plasma: brain concentrations in controls and patients with Alzheimer's disease.
A novel pituitary protein, designated as 7B2, recently purified in our laboratory was measured using a specific radioimmunoassay in conjunction with immuno-affinity extraction, in cerebrospinal fluid (CSF) and in plasma obtained from normal volunteers. The mean concentrations of immunoreactive (IR)-7B2 were 2154 pg/ml in CSF and 29 pg/ml in plasma. Studies by SDS-poly-acrylamide gel electrophoresis revealed that both CSF IR-7B2 and plasma IR-7B2 have an apparent molecular weight of around 20,000-21,000 as previously observed in various rat tissues. IR-7B2 was also measured in various brain regions obtained from control subjects and patients with Alzheimer's disease. IR-7B2 was widely distributed in the human brain, with the highest concentrations in substantia nigra and caudate. IR-7B2 brain concentrations were found to be similar between control subjects and patients with Alzheimer's disease. Gel permeation chromatography of extracts of various brain regions revealed two major peaks with apparent molecular weights of 45,000-50,000 and 11,000-16,000 in hypothalamus, caudate, frontal cortex, hippocampus, putamen and locus coeruleus, and only one peak with an apparent molecular weight of 14,000-16,000 in substantia nigra and globus pallidus. These data suggest that this novel pituitary protein may play a role of consequence perhaps as a neurotransmitter or as a neuromodulator in the human central nervous system.