Evidence for a calcium-mobilizing receptor triggered by cadmium, or decreasing external pH or sodium in coronary endothelial cells

Conference · Mon Feb 26 00:00:00 EST 1990 · FASEB Journal (Federation of American Societies for Experimental Biology); (United States)

OSTI ID:5488241

Dwyer, S D; Zhuang, Yingxin; Smith, L; Smith, J B ^[1]

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1. Univ. of Alabama, Birmingham (United States)

Cadmium (1 {mu}M) or decreasing external pH (pH{sub o}) or Na concentration (Na{sub o}) transiently increased cytoplasmic free Ca (Ca{sub i}) by {approximately}5-fold as measured with fura-2 in endothelial cells grown on cover glasses. Cd or pH{sub o}=6 evoked similar peak Ca{sub i} increases in the presence or absence of external Ca indicating that they trigger the release of stored Ca. Cd or 4 mM Na{sub o}, but not pH{sub o} 6, caused sustained Ca{sub i} increases. The sustained phase of the Ca{sub i} response to Cd required external Ca. Decreasing intracellular pH with propionate had no effect on Ca{sub i}. Cd and some other divalent metals also stimulated 45Ca efflux. The potency order of the metals that stimulated efflux was Cd > Co > Ni > Fe(II) > Mn. Cd apparently acts at an extracellular site because loading the cells with a heavy metal chelator (TPEN) only slightly affected Cd- or ATP-stimulated 45Ca efflux. Addition of Zn or Cu(II) to the assay solution prevented the stimulation of efflux by Cd and had no effect on ATP-evoked efflux. Decreasing Na{sub o} stimulated 45Ca efflux {approximately}4-fold and slightly increased 45Ca influx. Decreasing Na{sub o} to 27 mM or pH{sub o} to 6.4 half-maximally increased 45Ca efflux. The stimulation of efflux was independent of external Ca or the osmotic Na substitute. The release of stored Ca, not Ca influx via Na-Ca exchange, causes the increase in Ca{sub i} and 45Ca efflux evoked by decreasing Na{sub o}. Incubating the cells with Zn prior to assaying efflux in the absence of Zn strongly inhibited the stimulation of 45Ca efflux by Cd, pH{sub o} 6, and the Na{sub o} removal. Desensitization by Zn had no effect on ATP-stimulated efflux. These finding support the hypothesis proposed previously that the trace metals or decreasing external Na or pH release stored Ca by stimulating the same cell surface receptor.

• OSTI ID: 5488241
• Report Number(s): CONF-9004153-; CODEN: FAJOE
• Journal Information: FASEB Journal (Federation of American Societies for Experimental Biology); (United States), Vol. 4:3; Conference: 74. annual meeting of the Federation of American Societies for Experimental Biology, Washington, DC (United States), 1-5 Apr 1990; ISSN 0892-6638
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CADMIUM
BIOLOGICAL EFFECTS
CALCIUM
BIOCHEMICAL REACTION KINETICS
ANIMAL CELLS
CALCIUM 45
COBALT
ENDOTHELIUM
HEART
IRON
MANGANESE
NICKEL
PH VALUE
RADIORECEPTOR ASSAY
RECEPTORS
SODIUM
ALKALI METALS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMAL TISSUES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CARDIOVASCULAR SYSTEM
DAYS LIVING RADIOISOTOPES
ELEMENTS
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MEMBRANE PROTEINS
METALS
NUCLEI
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
TISSUES
TRACER TECHNIQUES
TRANSITION ELEMENTS
550301* - Cytology- Tracer Techniques