Kinetics of binding of dihydropyridine calcium channel ligands to skeletal muscle membranes: Evidence for low-affinity sites and for the involvement of G proteins

Journal Article · Tue Jun 11 00:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00237a012· OSTI ID:5081108

Dunn, S M.J.; Bladen, C ^[1]

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1. Univ. of Alberta, Edmonton (Canada)

Detailed kinetic studies of the binding of the calcium channel antagonist (+)-({sup 3}H)PN200-110 to membrane preparations form rabbit skeletal muscle have demonstrated that, in addition to the high-affinity sites that are readily measured in equilibrium and kinetic experiments, there are also dihydropyridine binding sites with much lower affinities. These sites were detected by the ability of micromolar concentrations of several dihydropyridines to accelerate the rate of dissociation of (+)-({sup 3}H)PN200-110 from its high-affinity sites. The observed increase in rate was dependent on the concentration of competing ligand, and half-maximal effects occurred at approximately 10 {mu}M for the agonist ({plus minus})-Bay K8644 and for the antagonists nifedipine, ({plus minus})-nitrendipine, and (+)-PN200-110. The low-affinity sites appear to be stereospecific since ({minus})-PN200-110 (1-200 {mu}M) did not affect the dissociation rate. The possible involvement of guanine nucleotide binding proteins in dihydropyridine binding has been investigated by studying the effects of guanosine 5'-O-(3-thiotriphosphate) (GTP{gamma}S) and guanosine 5'-O-(2-thiodiphosphate) (GDP{beta}S) on binding parameters. GTP{gamma}S did increase the ability of ({plus minus})-({sup 3}H)PN200-110. These results suggest that skeletal muscle dihydropyridine receptors have low-affinity binding sites that may be involved in the regulation of calcium channel function and that activation of a guanine nucleotide binding protein may modulate the binding of agonists but not of antagonists to these sites.

• OSTI ID: 5081108
• Journal Information: Biochemistry; (United States), Vol. 30:23; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
MEMBRANE PROTEINS
BIOCHEMICAL REACTION KINETICS
PYRIDINES
CELL MEMBRANES
GUANINE
LIGANDS
MICROSOMES
MUSCLES
NUCLEOTIDES
RABBITS
TRITIUM COMPOUNDS
AMINES
ANIMALS
AROMATICS
AZAARENES
AZINES
CELL CONSTITUENTS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
KINETICS
MAMMALS
MEMBRANES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PROTEINS
PURINES
REACTION KINETICS
RIBOSOMES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques