title: Glial cell line-derived neurotrophic factor does not enter normal mouse brain.
abstract: Glial cell line-derived neurotrophic factor (GDNF) is produced both in the central nervous system (CNS) and the periphery. Effective in ameliorating neurodegeneration in several animal models of CNS disease, its promise as a therapeutic agent would be greatly enhanced if it readily crossed the blood-brain barrier (BBB) in unmodified form. Here, we used the sensitive techniques of multiple-time regression analysis and ex-vivo perfusion in blood-free buffer to examine the entry of (125)I-GDNF into mouse brain. The integrity of GDNF in blood and brain was examined by high performance liquid chromatography and the physicochemical properties determining permeability were measured by octanol/buffer partition coefficient and hydrogen bonding. The efflux of (125)I-GDNF was determined to test for the presence of a bidirectional transport system. The results show that (125)I-GDNF differs from other peptides and polypeptides in that it does not enter brain any faster than (99m)Tc-albumin, an effect that cannot be explained by degradation, rapid efflux, protein binding, or inadequate lipophilicity. Thus, GDNF shows a different type of interaction with the BBB. In normal mice, the BBB functions as a substantial physical barrier; in pathological or traumatic situations when the barrier is partially disrupted, the lack of restriction by a saturable transport system could make GDNF a suitable candidate for peripheral delivery in promoting neuroregeneration.
authors.affiliation: VA Medical Center and Tulane University School of Medicine, 1601 Perdido Street, New Orleans, LA 70112-1262, USA. peptides@tulane.edu
authors.forename: Abba J
authors.initials: AJ
authors.lastname: Kastin
authors.forename: Victoria
authors.initials: V
authors.lastname: Akerstrom
authors.forename: Weihong
authors.initials: W
authors.lastname: Pan
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D051100:Glial Cell Line-Derived Neurotrophic Factor; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009414:Nerve Growth Factors / Q000378:metabolism*; D012709:Serum Albumin / Q000378:metabolism
chemical_list: C495040:Gdnf protein, mouse; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D012709:Serum Albumin