Characterization of histamine receptors in isolated pig basilar artery by functional and radioligand binding studies

Journal Article · Thu Dec 31 23:00:00 EST 1992 · Life Sciences; (United States)

DOI:https://doi.org/10.1016/0024-3205(93)90570-S· OSTI ID:5577392

Miyamoto, Atsushi; Nishio, Akira ^[1]

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1. Kagoshima Univ. (Japan)

Histamine receptors in pig basilar arteries were investigated in vitro by radioligand binding assays and by measuring the contractile and relaxant responses to histamine. Histamine and 2-pyridyethylamine (H[sub 1]-agonist) induced concentration-dependent contractions, whereas impromidine (H[sub 2]-agonist) induced concentration-dependent relaxations. These responses were independent of the presence of endothelial cells. Diphenhydramine (H[sub 1]-antagonist) partially reversed the histamine-induced contractions to relaxations. Cimetidine (H[alpha][sub 2]-antagonist) potentiated the contraction in a concentration-dependent manner. In the presence of cimetidine, the pEC[sub 50] value of histamine for the contraction was 6.30, and diphenhydramine competitively antagonized the histamine-induced contractions (pA[sub 2], 7.77). In the presence of diphenhydramine, the pEC[sub 50] value of histamine for the relaxation was 5.93, and cimetidine competitively antagonized the histamine-induced relaxations (pA[sub 2], 6.62). In the binding studies, the K[sub d] value of [[sup 3]H]mepyramine was 2.1 nM and the B[sub max] value was 95.6 fmol/mg protein. A competition experiment with diphenhydramine showed that the pK[sub i] value (7.51) was similar to the pA[sub 2] value. The K[sub d] value for [[sup 3]H]cimetidine was 126.0 nM and the B[sub max] value was 459.8 fmol/mg protein. The pK[sub d] (6.90) for [[sup 3]H]cimetidine was similar to the pA[sub 2] for cimetidine. The Hill coefficients for these experiments were not significantly different from unity. The present findings indicate that the number of H[sub 1]-receptors, in terms of the B[sub max] value for [[sup 3]H]mepyramine, is smaller than that of H[sub 2]-receptors, in terms of the B[sub max] value for [[sup 3]H]cimetidine. However, the contractile response to histamine is predominantly mediated through stimulation of H[sub 1]-receptors on vascular smooth muscle cells in pig basilar artery.

• OSTI ID: 5577392
• Journal Information: Life Sciences; (United States), Journal Name: Life Sciences; (United States) Vol. 53:16; ISSN 0024-3205; ISSN LIFSAK
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400101* -- Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures
AMINES
ANIMALS
ARTERIES
AZOLES
BLOOD VESSELS
BODY
CARDIOVASCULAR SYSTEM
CHEMICAL ANALYSIS
DOMESTIC ANIMALS
DRUGS
HETEROCYCLIC COMPOUNDS
HISTAMINE
HYDROGEN COMPOUNDS
IMIDAZOLES
IN VITRO
LABELLED COMPOUNDS
LIGANDS
MAMMALS
MEMBRANE PROTEINS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PROTEINS
QUANTITATIVE CHEMICAL ANALYSIS
RADIOCHEMICAL ANALYSIS
RADIOPHARMACEUTICALS
RECEPTORS
SWINE
TRITIUM COMPOUNDS
VERTEBRATES