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Title: Absorptive-mediated endocytosis of cationized albumin and a beta-endorphin-cationized albumin chimeric peptide by isolated brain capillaries. Model system of blood-brain barrier transport

Cationized albumin (pI greater than 8), unlike native albumin (pI approximately 4), enters cerebrospinal fluid (CSF) rapidly from blood. This suggests that a specific uptake mechanism for cationized albumin may exist at the brain capillary wall, i.e. the blood-brain barrier. Isolated bovine brain capillaries rapidly bound cationized (/sup 3/H)albumin and approximately 70% of the bound radioactivity was resistant to mild acid wash, which is assumed to represent internalized peptide. Binding was saturable and a Scatchard plot gave a maximal binding capacity (Ro) = 5.5 +/- 0.7 micrograms/mgp (79 +/- 10 pmol/mgp), and a half-saturation constant (KD) = 55 +/- 8 micrograms/ml (0.8 +/- 0.1 microM). The binding of cationized (/sup 3/H)albumin (pI = 8.5-9) was inhibited by protamine, protamine sulfate, and polylysine (molecular weight = 70,000) with a Ki of approximately 3 micrograms/ml for all three proteins. The use of cationized albumin in directed delivery of peptides through the blood-brain barrier was examined by coupling (/sup 3/H)beta-endorphin to unlabeled cationized albumin (pI = 8.5-9) using the bifunctional reagent, N-succinimidyl 3-(2-pyridyldithio)proprionate. The (/sup 3/H)beta-endorphin-cationized albumin chimeric peptide was rapidly bound and endocytosed by isolated bovine brain capillaries, and this was inhibited by unlabeled cationized albumin but not by unconjugated beta-endorphin ormore » native bovine albumin. Cationized albumin provides a new tool for studying absorptive-mediated endocytosis at the brain capillary and may also provide a vehicle for directed drug delivery through the blood-brain barrier.« less
Authors:
; ;
Publication Date:
OSTI Identifier:
5786579
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Biol. Chem.; (United States); Journal Volume: 262:31
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; ALBUMINS; MEMBRANE TRANSPORT; PEPTIDES; BIOCHEMICAL REACTION KINETICS; AUTORADIOGRAPHY; BLOOD-BRAIN BARRIER; BRAIN; CAPILLARIES; CATIONS; CATTLE; INHIBITION; PHAGOCYTOSIS; PROTAMINES; TRITIUM COMPOUNDS; ANIMALS; BLOOD VESSELS; BODY; CARDIOVASCULAR SYSTEM; CENTRAL NERVOUS SYSTEM; CHARGED PARTICLES; COAGULANTS; DOMESTIC ANIMALS; DRUGS; HEMATOLOGIC AGENTS; HEPARIN ANTAGONISTS; IONS; KINETICS; LABELLED COMPOUNDS; MAMMALS; NERVOUS SYSTEM; NUCLEOPROTEINS; ORGANIC COMPOUNDS; ORGANS; PROTEINS; REACTION KINETICS; RUMINANTS; VERTEBRATES 550201* -- Biochemistry-- Tracer Techniques