AJP - Heart and Circulatory Physiology, Vol 259, Issue 5 1343-H1350, Copyright © 1990 by American Physiological Society
Quantitative and autoradiographic analyses of alpha-adrenergic and serotonergic receptors on aorta and coronary artery
H. Tsutsui, H. Tomoike and M. Nakamura
Research Institute of Angiocardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Norepinephrine, epinephrine, and 5-hydroxytryptamine (5-HT) modulate the
vascular tone via specific receptors on the vascular wall. Binding
characteristics and localization of alpha-adrenergic and serotonergic
receptors were determined in porcine aortas and coronary arteries.
Radioligand binding studies were done using frozen sections of vascular
tissue (10 microns thick), and the obtained data were compared with
findings on microsomal fractions prepared from smooth muscle cells.
Affinities [dissociation constant (Kd)] of 125I-labeled
2-[beta-(4-hydroxyphenyl)-ethylaminomethyl]-tetralone (BE 2254), an alpha
1-antagonist, for alpha-adrenergic receptors on aortic and coronary
microsomal fractions were 190 and 224 pM, respectively. The Kd of
125I-labeled lysergic acid diethylamide (LSD), a serotonergic antagonist,
to serotonergic receptors on the aorta was 403 pM, a value less than that
obtained for the coronary artery (873 pM, p less than 0.01). The Kd of
125I-BE 2254 on tissue sections from the aorta was 164 pM and did not
significantly differ from that obtained for microsomal fractions.
Inhibition constants of adrenergic agonists and antagonists for specific
125I-BE 2254 binding on aortic sections were identical with those obtained
for microsomal fractions. Receptor densities examined by 125I-BE 2254 and
125I-LSD were higher in the aorta than in the coronary artery. 125I-BE 2254
bound specifically to alpha 1-adrenergic and 125I-LSD to 5-HT1-like
receptors. Radiodensities of 125I-BE 2254 and 125I-LSD were homogeneous
macroscopically across the aortic media. Silver grains distributed
homogeneously over the smooth muscle cells across the media. There was no
accumulation of silver grains to the intima.(ABSTRACT TRUNCATED AT 250
WORDS)
