Voltage-dependent calcium channels in skeletal muscle transverse tubules. Measurements of calcium efflux in membrane vesicles

Journal Article · Wed Jul 05 00:00:00 EDT 1989 · Journal of Biological Chemistry; (USA)

OSTI ID:5641768

Dunn, S M ^[1]

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1. Univ. of Iowa, Iowa City (USA)

Transverse tubule membranes isolated from rabbit skeletal muscle consist mainly of sealed vesicles that are oriented primarily inside out. These membranes contain a high density of binding sites for 1,4-dihydropyridine calcium channel antagonists. The presence of functional voltage-dependent calcium channels in these membranes has been demonstrated by their ability to mediate {sup 45}Ca2+ efflux in response to changes in membrane potential. Fluorescence changes of the voltage-sensitive dye, 3,3'-dipropyl-2,2'-thiadicarbocyanine, have shown that transverse tubule vesicles may generate and maintain membrane potentials in response to establishing potassium gradients across the membrane in the presence of valinomycin. A two-step procedure has been developed to measure voltage-dependent calcium fluxes. Vesicles loaded with {sup 45}Ca2+ are first diluted into a buffer designed to generate a membrane potential mimicking the resting state of the cell and to reduce the extravesicular Ca2+ to sub-micromolar levels. {sup 45}Ca2+ efflux is then measured upon subsequent depolarization. Flux responses are modulated with appropriate pharmacological specificity by 1,4-dihydropyridines and are inhibited by other calcium channel antagonists such as lanthanum and verapamil.

• OSTI ID: 5641768
• Journal Information: Journal of Biological Chemistry; (USA), Vol. 264:19; ISSN 0021-9258
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CALCIUM
MEMBRANE TRANSPORT
PORINS
BIOCHEMICAL REACTION KINETICS
CALCIUM 45
CELL MEMBRANES
EDTA
ENZYME INHIBITORS
FLUORESCENCE
LANTHANUM
MUSCLES
OXADIAZOLES
POTASSIUM
PYRIDINE
RABBITS
TRACER TECHNIQUES
ALKALI METALS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
AMINO ACIDS
ANIMALS
AZINES
AZOLES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM ISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHELATING AGENTS
DAYS LIVING RADIOISOTOPES
ELEMENTS
EVEN-ODD NUCLEI
HETEROCYCLIC COMPOUNDS
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LUMINESCENCE
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
METALS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PROTEINS
PYRIDINES
RADIOISOTOPES
RARE EARTHS
REACTION KINETICS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques