Blood-nerve transfer of albumin and its implications for the endoneurial microenvironment.
Blood-nerve transfer of plasma albumin was studied by measuring the permeability coefficient-surface area (PS) product of the blood-nerve barrier (BNB) to 125I-albumin in rat sciatic nerve using the i.v. bolus injection method. The calculated PS was 6.3 +/- 0.5 (S.E.M.) x 10(-7) ml.g-1.s-1. This value is smaller by more than an order of magnitude of that measured for sucrose and confirms the relative impermeance of the BNB to blood-borne solutes. From a review of the available evidence, it is concluded that normal blood-nerve exchange occurs predominantly across the endoneurial microvasculature, and the PS of the BNB reflects the permeability of capillaries to a greater extent than that of the perineurium. The only capillaries found to be less permeable than these are the cerebral capillaries. Proximo-distal differences (sciatic vs tibial) of the PS could not be detected. Blood-nerve albumin transfer was calculated at 1.2 mg.g-1.day-1, and the daily turnover of endoneurial albumin to be about 30%. It is postulated that small increases in PS of BNB to albumin lead to an elevation of endoneurial albumin concentration and, through the operation of Starling forces, subsequently produce endoneurial oedema. A major question posed by the results of this study is the identity of pathways for clearance of albumin and other macromolecules from the endoneurium.
Department of Neurology, Mayo Clinic, Rochester, MN 55905.
A
A
Weerasuriya
G L
GL
Curran
J F
JF
Poduslo
D000818:Animals; D002199:Capillary Permeability; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012584:Sciatic Nerve / Q000098:blood supply* / Q000378:metabolism; D012709:Serum Albumin / Q000493:pharmacokinetics*
D012709:Serum Albumin