AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 1 224-R230, Copyright © 1989 by American Physiological Society
Adrenergic receptors on cerebral microvessels: pericyte contribution
R. M. Elfont, P. R. Sundaresan and C. D. Sladek
Department of Neurobiology, University of Rochester Medical Center, New York 14642.
R224-R230, 1989.--[125I]iodocyanopindolol ([125I]ICYP) and [3H]rauwolscine
were used to quantitate, respectively, the beta- and alpha 2-adrenergic
receptors in freshly isolated bovine cerebral microvessels and in pericyte
cultures derived from these microvessels. Morphological and
immunocytochemical criteria distinguished the pericytes from endothelial
cells. Competitive binding studies established the specificity of the
radioligand binding. The maximal number of binding sites (Bmax) for
[125I]ICYP in the pericytes constituted only 8% of that in the microvessels
(3.5 +/- 1.3 vs. 44.4 +/- 6.6 fmol/mg protein). In contrast, the Bmax for
[3H]rauwolscine in the pericytes was 50% of that in the microvessels (55.4
+/- 11.8 vs. 111.1 +/- 9.5 fmol/mg protein). The dissociation constants for
both [125I]ICYP and [3H]rauwolscine were similar in the two preparations.
No alpha 1-adrenergic receptors, as defined by the specific binding of
[3H]prazosin, were identified either in the pericytes or microvessels.
Overall, our results suggest that pericytes contribute minimally to the
total beta-adrenoceptor number of cerebral microvessels, and thus the
beta-adrenoceptors must be located predominantly on endothelial cells.
However, the contribution of pericytes to the total alpha 2-adrenoceptor
number of the microvessels may be substantial.
