Journal of Applied Physiology, Vol 77, Issue 3 1081-1086, Copyright © 1994 by American Physiological Society
Protein accumulation in cerebrospinal fluid during -90 degrees head-down tilt in rabbit
T. S. Wen, D. C. Randall and J. F. Zolman
Department of Physiology, University of Kentucky, Lexington 40536-0084.
Plasma proteins are only somewhat larger than the intercellular spaces of
the cerebral microvessels that constitute the blood-brain barrier or of the
choroid plexus villi that elaborate cerebrospinal fluid (CSF). We
hypothesized that the integrity of these barriers in anesthetized rabbits
might be compromised during head-down tilt (HDT). Plasma protein and
osmolality, hematocrit, and CSF protein concentration were compared in
rabbits exposed to 1 h of HDT (n = 20) and prone rabbits (n = 10). In
addition, the concentration of trypan blue dye, injected intravenously at
the end of HDT or the prone position, was measured in brain homogenate.
Finally, arterial blood pressure was measured via a catheterized carotid
artery. HDT disrupted the barrier between blood and CSF, as indicated by a
significantly (P < 0.01) greater brain trypan blue concentration in the
HDT rabbits [172.2 +/- 14.4 (SD) micrograms/g dry wt] than in the prone
rabbits (29.8 +/- 4.4 micrograms/g dry wt). Moreover CSF protein 5 min
after HDT onset was significantly increased compared with control in HDT
rabbits (54.6 +/- 1.9 vs. 81.4 +/- 5.2 mg/dl; n = 8) but not in prone
rabbits (55.6 +/- 2.7 vs. 57.2 +/- 5.0 mg/dl; n = 6). Changes in the plasma
protein-to-hematocrit ratio in the HDT animals, but not in the prone
animals, were also compatible with a loss of fluid from the vascular
compartment.(ABSTRACT TRUNCATED AT 250 WORDS)
