Additive competitive interaction of verapamil and quinidine at alpha-adrenergic receptors of isolated cardiac guinea pig myocytes and human platelets

Journal Article · Fri Jan 01 00:00:00 EST 1988 · Life Sci.; (United States)

DOI:https://doi.org/10.1016/0024-3205(88)90458-4· OSTI ID:5515933

Mueller, A; Noack, E

Recent clinical work has questioned the safety of a combined therapy of oral quinidine and intravenenous verapamil, because some patients were reported to react with severe hypotension probably due to drug interactions with vascular alpha-adrenergic receptors. In order to obtain further quantitative information on the underlying mechanism, the authors used the radioligands (/sup 3/H)-prazosin and (/sup 3/H)-yohimbine to perform binding studies on intact cells, with predominantly alpha-1 (isolated myocytes) or alpha-2 subtypes (human platelets) of adrenergic receptors. Their studies confirm that both verapamil and quinidine possess a distinct alpha-adrenergic receptor blocking activity and do not discriminate between the alpha-1 and alpha-2 subtype. Their interaction was competitive and in the presence of both drugs inhibition of radioligand binding was additive. The alpha-adrenergic blockade by verapamil was stereospecific as D-verapamil increased the dissociation constant of the radioligand to a much lesser degree than L-verapamil. The calcium channel blocker nitrendipine, a 1,4-dihydropyridine derivative, did not show any competition up to concentrations of 10 ..mu..mol/l. 26 references, 5 figures, 1 table.

• Research Organization: Universitaet Duesseldorf, Germany, F.R.
• OSTI ID: 5515933
• Journal Information: Life Sci.; (United States), Vol. 42:6
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
PORINS
BIOCHEMICAL REACTION KINETICS
SYMPATHOMIMETICS
RECEPTORS
BLOOD PLATELETS
ENZYME INHIBITORS
EXPERIMENTAL DATA
GUINEA PIGS
HEART
LIGANDS
MAN
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY
BODY FLUIDS
CARDIOVASCULAR SYSTEM
DATA
DRUGS
INFORMATION
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MATERIALS
MEMBRANE PROTEINS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANS
PRIMATES
PROTEINS
REACTION KINETICS
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques