Protein accumulation in cerebrospinal fluid during -90 degrees head-down tilt in rabbit.
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)
Department of Physiology, University of Kentucky, Lexington 40536-0084.
T S
TS
Wen
D C
DC
Randall
J F
JF
Zolman
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001798:Blood Proteins / Q000134:cerebrospinal fluid*; D001812:Blood-Brain Barrier; D003228:Conjunctiva / Q000473:pathology; D006112:Gravitation; D018475:Head-Down Tilt / Q000502:physiology*; D006400:Hematocrit; D016684:Prone Position / Q000502:physiology; D011485:Protein Binding; D011817:Rabbits; D014343:Trypan Blue
D001798:Blood Proteins; D014343:Trypan Blue