Journal of Applied Physiology, Vol 73, Issue 3 918-924, Copyright © 1992 by American Physiological Society
Technique-dependent variations in cerebral microvessel blood volumes and hematocrits in the rat
D. Bereczki, L. Wei, V. Acuff, K. Gruber, A. Tajima, C. Patlak and J. Fenstermacher
Department of Neurological Surgery, State University of New York, Stony Brook 11794-8122.
To quantitate small parenchymal microvessel blood volumes in the brain, the
distribution spaces of radiolabeled red blood cells (RBC) and serum albumin
(RISA) were assessed in rats by different methods of tissue sampling and
radioassay. Three minutes after intravenous administration of 55Fe-RBCs
and/or 125I-RISA, the rats were decapitated. The brain was either
immediately frozen within the skull and later removed (head-frozen group)
or rapidly removed from the skull and then frozen (brain-frozen group).
Radioactivity was measured either by liquid scintillation counting of
tissue pieces, which contained pial plus large and small parenchymal
microvessels, or by quantitative autoradiography (QAR) of tissue sections,
which indicated small parenchymal microvessel blood only. In 12 of 15
areas, the RISA, RBC, and blood volumes determined by liquid scintillation
counting of head-frozen tissue pieces were equal to or greater than those
of brain-frozen tissue; this indicated less than or equal to 25% greater
blood retention in pial and parenchymal microvessels with head freezing. At
the parenchymal microvessel level (QAR assay), the distribution volumes of
RBCs, RISA, and blood were similar with the two freezing techniques; hence
with QAR either freezing procedure can be used to assess small parenchymal
microvessel blood volumes.
