Two saturable recognition sites for (-) (125I)iodo-N6-(4-hydroxyphenyl-isopropyl)-adenosine binding on purified cardiac sarcolemma

Journal Article · Wed Jan 01 00:00:00 EST 1986 · J. Receptor Res.; (United States)

DOI:https://doi.org/10.3109/10799898609074817· OSTI ID:6704563

Hausleithner, V; Freissmuth, M; Schuetz, W

Analysis of (-) (125)iodo-N6-(4-hydroxyphenylisopropyl)-adenosine (( /sup 125/I)HPIA) binding to purified sarcolemmal preparations of guinea pig and bovine hearts revealed two classes of binding sites when unlabeled iodo-HPIA (100 mumol/l) was used as non-specific binding marker. In the presence of 1 mmol/l theophylline, however, only the high affinity component was detected. Adenosine receptor agonists caused biphasic displacement of (/sup 125/I)HPIA binding, with a high affinity potency rank order typical of interaction with A1-adenosine receptors. Biphasic competition curves were also observed with 8-phenyltheophylline and isobutylmethylxanthine, whereas the theophylline curve was monophasic up to 1 mmol/l. In brain membranes, specific binding of (/sup 125/I)HPIA as well as of (/sup 3/H)PIA was further reduced when unlabeled iodo-HPIA replaces theophylline as the non-specific binding marker. These results suggest the presence of two (/sup 125/I)HPIA binding sites on cardiac sarcolemma and brain membranes, but receptor function can only be ascribed to the high affinity sites. The low affinity site probably represents an artefact, which is often observed when non-specific binding is defined with the unlabeled counterpart or a structurally related ligand of the radioligand used.

• Research Organization: Univ. of Vienna, Austria
• OSTI ID: 6704563
• Journal Information: J. Receptor Res.; (United States), Vol. 3-4
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ADENOSINE
RECEPTORS
BRAIN
CATTLE
CELL MEMBRANES
GUINEA PIGS
HEART
IODINE 125
LABELLED COMPOUNDS
MYOCARDIUM
RADIORECEPTOR ASSAY
THEOPHYLLINE
ANIMALS
AROMATICS
AZAARENES
BETA DECAY RADIOISOTOPES
BODY
CARDIOVASCULAR AGENTS
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CENTRAL NERVOUS SYSTEM
DAYS LIVING RADIOISOTOPES
DOMESTIC ANIMALS
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
HETEROCYCLIC COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
MUSCLES
NERVOUS SYSTEM
NUCLEI
NUCLEOSIDES
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANS
PROTEINS
PURINES
RADIOISOTOPES
RIBOSIDES
RODENTS
RUMINANTS
TRACER TECHNIQUES
VASODILATORS
VERTEBRATES
XANTHINES
550201* - Biochemistry- Tracer Techniques