Stoichiometry of Na/Ca antiport obtained by magnesium inhibition in cultured vascular smooth muscle cells

Conference · Fri May 01 04:00:00 EDT 1987 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5727408

Smith, J B; Higgins, B L; Smith, L

Cultured smooth muscle cells from rat aorta were loaded with Na, and Na/Ca antiport was assayed by measuring the initial rates of /sup 45/Ca influx and /sup 22/Na efflux. The replacement of extracellular Na with other monovalent ions, usually N-methyl-D-glucamine (NMG), was essential for obtaining significant antiport activity. Mg competitively inhibited /sup 45/Ca influx via the antiporter (Ki = 100 uM). External Ca stimulated /sup 22/Na efflux as expected for antiport activity. Mg did not stimulate /sup 22/Na efflux indicating that Mg is not transported by the antiporter. Mg inhibited Ca-stimulated /sup 22/Na efflux as expected from the /sup 45/Ca influx data. The stoichiometry of the antiporter was calculated from the changes in the rates of /sup 45/Ca influx and /sup 22/Na efflux at 3 Mg concentrations: 2.87 +/- 0.25 (mean +/- SE, n=5). The replacement of external NMG with potassium, but not other monovalent ions (choline, Li), decreased the potency of Mg as an inhibitor of Na/Ca antiport by about 6 fold. Other divalent cations (Co, Mn, Cd, Ba) inhibited Na/Ca antiport and high external potassium decreased the potency of each by about 6 fold. The order of effectiveness of the divalent cations as inhibitors of Na/Ca antiport (Cd>Mn>Co>Ba>Mg) correlated with the crystal ionic radius of the cation.

• Research Organization: Univ. of Alabama, Birmingham
• OSTI ID: 5727408
• Report Number(s): CONF-870644-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 46:6
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
560300 -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALCOHOLS
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
AMINES
AMMONIUM COMPOUNDS
ANIMAL CELLS
ANIMALS
BARIUM COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CADMIUM COMPOUNDS
CALCIUM 45
CALCIUM ISOTOPES
CARBOHYDRATES
CATIONS
CHARGED PARTICLES
CHOLINE
COBALT COMPOUNDS
DAYS LIVING RADIOISOTOPES
DRUGS
EVEN-ODD NUCLEI
GLUCOSAMINE
HEXOSAMINES
HEXOSES
HYDROXY COMPOUNDS
INHIBITION
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LIPOTROPIC FACTORS
LITHIUM COMPOUNDS
MAGNESIUM COMPOUNDS
MAMMALS
MANGANESE COMPOUNDS
MEMBRANE TRANSPORT
MONOSACCHARIDES
MUSCLES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
POTASSIUM COMPOUNDS
QUATERNARY COMPOUNDS
RADIOISOTOPES
RATS
RODENTS
SACCHARIDES
SODIUM 22
SODIUM COMPOUNDS
SODIUM ISOTOPES
TRACER TECHNIQUES
TRANSITION ELEMENT COMPOUNDS
VERTEBRATES
YEARS LIVING RADIOISOTOPES