ヒトにおける免疫学的β-エンドルフィンの脳内分布
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概要
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β-Endorphin (β-EP) is known to be the most potent among the opioid peptides present in human and animal brains. However, the significance and physiological role of β-EP remain unknown so far. Therefore, to obtain a clue about its function in human, extracts of discrete areas of human brain and pituitary were radioimmunoassayed for β-EP and ACTH contents. The concentration of immunoreactive β-EP was highest in the pituitary (anterior and posterior lobe combined together) (16.1 ng/mg weight {w.w.}), followed by pedunculus cerebellaris superior (226± 104 pg/mg w.w.) (mean±SEM), nucleus ruber (220±65.9 pg/mg w.w.), pyramis (191±93.9 pg/mg w.w.), corpus callosum (182±87.5 pg/mg w.w.), nucleus dentatus (145±80.3 pg/mg w.w.), globus pallidus (138±61.8 pg/mg w.w.), pedunculus cerebellaris inferior (135±111 pg/mg w.w.), capsula interna(120±67.1 pg/mg w.w.), nucleus subthalamicus (107±70.5 pg/mg w.w.), hypothalamus (102±38.5 pg/mg w.w.), crus cerebri (88.4±83.5 pg/mg w.w.) and nucleus olivaris (87.8±41.5 pg/mg w.w.). Almost as similar as observed with β-EP, immunoreactive ACTH content was highest in the pituitary then followed by limbic systems, pyramidal and extrapyramidal systems and so forth. By gel chromatography on a Sephadex G-50 superfine column (1×50 cm), immunoreactive β-EP of the pituitary eluted as three peaks, starting in the void volume corresponding to a common precursor, followed by β-LPH, whose peak was the largest, and β-EP. Chromatography of hypothalamus extracts gave rise to two peaks corresponding to a small component of β-LPH and a large one of β-EP. Pyramis extracts, chromatographed, showed a single peak between the elution position of <125>^I-β-LPH and that of <125>^I-β-EP while zona incerta extracts eluted as a peak in the void volume. Globus pallidus extracts showed three peaks corresponding to the fraction in the void volume, β-LPH, and β-EP, respectively. Crus cerebri extracts had two peaks ; small one in the void volume and large one in the same fraction of <125>^I-β-LPH. Pons extracts disclosed two peaks corresponding to β-LPH and β-EP while extracts of corpus callosum and capsula interna had a broad peak eluting over those of β-LPH and β-EP. These results suggest that immunoreactive β-EP is widely distributed in human brain and also that there is the size heterogeneity in β-EP immunoreactivity in the brain. However, whether immunoreactive β-EP eluting in the fraction corresponding or not necessarily corresponding to the three known components, a common precursor, β-LPH and β-EP are due to authentic β-EP, β-EP-related peptides or crossreactive substances present in human brain remains to be further elucidated.
- 神戸大学の論文