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Albumin transfer across the choroid plexus of South American opossum (Monodelphis domestica)

journal contribution
posted on 2023-05-16, 10:41 authored by Knott, GW, Dziegielewska, KM, Habgood, MD, Li, ZS, Norman SaundersNorman Saunders
1. Blood-cerebrospinal fluid (CSF) transfer of various exogenous albumins has been investigated in developing Monodelphis domestica (South American grey short-tailed opossum) and compared with the steady-state CSF:plasma ratios for endogenous (Monodelphis) albumin. Ratios for Monodelphis albumin and human albumin were similar and were the highest at postnatal day 5 (P5) (48.2 ± 4.4 and 40.6 ± 4.5%, respectively). The ratio for bovine albumin was similar to the steady-state ratio for Monodelphis albumin at P7-8 but became consistently lower than the Monodelphis albumin ratio at all other ages until P32-36 when all albumins tested attained a similar low ratio. The CSF:plasma ratio of chemically modified (succinylated) bovine albumin was always significantly lower than that of other albumins, except at the oldest age examined (P32-36). 2. Immunocytochemistry showed that within the brain, albumin was confined to the lumen and endothelial cells of blood vessels. In the choroid plexus only a small proportion (0.2-1.7% of the total cell number) of epithelial cells was positive for albumin, both endogenous and exogenous, at all ages studied (except the 3rd ventricle where cells were only positive from P8). The CSF was strongly positive for all albumins. The peak proportion of positive cells and of albumin concentrations in CSF occurred at P8. These findings suggest that the primary route for penetration of albumin into CSF is directly across the choroid plexus rather than via the brain. 3. Double-labelling immunocytochemistry revealed that the same epithelial cells contained both endogenous (Monodellhis) and exogenous (human) albumin. In contrast, for succinylated albumin, at P7 only about 35% (lateral ventricle) and 50% (4th vetricle) of Momodelphis albumin-positive cells were also positive for succinylated albumin, but by P30 this proportion increased to 90% at both sites. 4. Thus the developing choroid plexus distinguishes between different albumins. Chemical modification of albumin (succinylation) disrupts this mechanism. It is proposed that in older animals (P32-36) all of the albumin in the CSF is derived from plasma by diffusion (as in adult animals). At earlier stages of development, a proportion of the albumin in CSP also appears to be transferred from the plasma by diffusion with an additional component transferred by a mechanism that can distinguish between different species of albumin. The main route of entry of albumin to CSF seems likely to be via the choroid plexus epithelial cells.

History

Publication title

Journal of Physiology

Volume

499

Pagination

179-194

ISSN

0022-3751

Department/School

Tasmanian School of Medicine

Publisher

Cambridge Univ Press

Place of publication

40 West 20Th St, New York, USA, Ny, 10011-4211

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the environmental sciences

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