Plasma membrane vesicles prepared from unadhered monocytes: Characterization of calcium transport and the calcium ATPase

Scully, Sean P.; Segel, George B.; Lichtman, Marshall A.

doi:10.1016/0143-4160(82)90042-2

Cited by 16 publications

(12 citation statements)

References 19 publications

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“…The increment in cytoplasmic calcium seen with exposure to 100 gg/ml Con A was 0.080 ,umol/liter cell water. In a previous report, we have shown that the calcium extrusion pump in the monocyte plasma membrane increases approximately twofold when the cytoplasmic free calcium is increased from 0.08 to 0.16 ,mol/liter cell water (16). This predicted increase in pump activity is consistent with the increase in the Ca exchange rate of 170% that we measured with radiolabeled calcium.…”

Section: Time (Min)supporting

confidence: 76%

“…Human mononuclear leukocytes were isolated from plateletpheresis residues ( 14) using an isopaque-ficoll step gradient ( 15). The monocytes were separated from the lymphocytes by counterflow centrifugal elutriation by first eluting the lymphocytes from the separation chamber, leaving behind a highly enriched monocyte population (16). The monocytes were eluted by increasing the rate of buffer flow through the separation chamber.…”

Section: Methodsmentioning

confidence: 99%

“…The binding of Con A increases the fraction of cell calcium that is available for exchange with the external media. The increment in free calcium plays a role in initiating superoxide production and monocyte activation and also accelerates the rate ofcalcium extrusion via the calcium transport ATPase ( 16). The calcium extrusion prevents any measurable change in total cell calcium and maintains calcium homeostasis.…”

Section: Time (Min)mentioning

confidence: 99%

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Calcium exchange and ionized cytoplasmic calcium in resting and activated human monocytes.

Scully¹,

Segel²,

Lichtman³

1984

J. Clin. Invest.

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A s bstract. We have performed a comprehensive study of calcium tracer flux, distribution, content, and ionized cytoplasmic calcium during monocyte activation. A model of monocyte calcium was developed from 45Ca uptake and exodus curves which indicated that cell calcium was partitioned between three compartments. The magnitude of the time constants for each pool lead us to propose cellular locations for these three compartments: a surface plasma membrane pool, a cytoplasmic pool, and an organelle pool. 45Ca uptake and exodus experiments were analyzed using a nonlinear least squares fit of compartmental exchange rates and sizes. The production of superoxide was used as a reflection ofthe state ofactivation ofthe monocytes treated with Concanavalin A (Con A). We found that Con A-treated monocytes have an increase in the calcium exchange rate with the cytoplasmic pool from 0.04 to 0.07/min (P < 0.05), and an increase in the size of the cytoplasmic pool from 0.08 to 0.13 pmol/cell (P < 0.05). There were no significant changes in the exchange rates or sizes associated with either of the other two compartments. The cytoplasmic ionized calcium was measured with the fluorescent probe, Quin 2, which indicated a resting level of 83 nM free calcium in unadhered monocytes. Con A stimulation caused a doubling of the cytoplasmic free calcium to 163 nM within 45 s. This increment in cytoplasmic free calcium preceded the onset of superoxide following Con A treatment. These studies indicate that Con A binding to the plasma membrane increases the monocyte plasma membrane permeability to calcium. External calcium en-

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Section: Time (Min)supporting

confidence: 76%

Section: Methodsmentioning

confidence: 99%

Section: Time (Min)mentioning

confidence: 99%

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Calcium exchange and ionized cytoplasmic calcium in resting and activated human monocytes.

Scully¹,

Segel²,

Lichtman³

1984

J. Clin. Invest.

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“…13 Mononuclear cell suspensions were sedimented at 200 g for 15 minutes and washed twice in 0.9% NaCI. Monocytes were resuspended in 15 ml of lysis medium (1 mM NaHCC>3,0.5 mM CaCt, pH 7.4) and disrupted in a homogenizer (25 strokes).…”

Section: Determination Of Plasma Membrane Fatty Acyl Contentmentioning

confidence: 99%

“…12 The present study was undertaken to investigate the effect of long-term dietary supplementation with unsaturated fatty acids in the form of com oil or with saturated fatty acids in the form of coconut oil with and without added cholesterol on mononuciear cell LDL degradation in Cebus albifrons monkeys. Animals maintained on diets rich in unsaturated fatty adds are known to have increased hepatic fractional catabolic rates for LDL 13 Thus, in the ex vivo setting we studied LDL degradation, membrane fluidity, and fatty acyl content in peripheral blood mononuciear cells as functional equivalents of hepatocytes. 1415 Our results indicate that dietary unsaturated fatty acids enhance cellular LDL degradation and that this effect is accompanied by cellular enrichment in these fatty adds and decreased membrane microviscosity.…”

mentioning

confidence: 99%

Effect of dietary fat saturation and cholesterol on low density lipoprotein degradation by mononuclear cells of Cebus monkeys.

et al. 1989

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The mechanism by which dietary unsaturated fatty acids lower low density lipoprotein (LDL) cholesterol Is unknown. Unsaturated fatty acids incorporated into the cell membrane can increase membrane fluidity and, as a result, dramatically alter membrane-dependent cell functions. Therefore, we examined the effect of long-term dietary consumption of com oil and coconut oil with and without cholesterol In amounts equivalent to those of a typical Western diet on the degradation of human LDL by peripheral blood mononuclear cells in Cebus alblfrons monkeys. Cellular LDL degradation was dramatically enhanced In the mononuclear cells Isolated from animals fed corn oil In comparison with those from animals fed coconut oil. The addition of cholesterol to the diets resulted in a slight attenuation of LDL degradation In the corn oil group while no effect was noted In the coconut oil group. Crossover E pidemiologic studies have linked diets rich In unsaturated fatty acids to a reduction in low density lipoprotein (LDL) cholesterol, 12 but the molecular mechanism by which this phenomenon occurs remains poorly understood. A number of possible mechanisms have been suggested, including modification in: 1) de novo cholesterol synthesis, 2) cholesterol absorption from the small intestine, 3) physicochemical properties of the LDL surface coat or core, 4) cholesterol distribution between plasma and various intrahepatic pools, 5) fecal sterol or cholesterol excretion, 6) partitioning of cholesterol among "cellular" pools, 7) apolipoprotein metabolism, and 8) rates of LDL metabolism.3 -7 Recent human and animal studies strongly support increased LDL metabolism as a This work was supported in part by NIH Grants RO1 HL40411, RO1-HL3610, and HL39385, by a Grant-in-Aid from the American Heart Association, a Fellowship Grant from the American Heart Association, Massachusetts Affiliate, and NIH-NRSA Grant F32-HL07700. Joseph Loscalzo is the recipient of a Career Development Award from the NIH (K04 HL02273).Address for correspondence: Joseph Loscalzo, M.D., Ph.D., Brigham and Women's Hospital,75 Francis Street, Boston, MA 02115.Received January 17, 1989; revision accepted July 5, 1989. major factor. 347 The actual cellular mechanism by which LDL clearance is enhanced, however, remains unknown.Alterations in the bulk physical properties of plasma membranes can produce changes in membranedependent cellular functions. Dietary fatty acids readily incorporate into cell membranes and can modify the physical properties of these membranes. Increasing c/s-unsaturated fatty acyl composition increases membrane fluidity (or decreases microviscosity and order), while increasing the saturated fatty acyl composition decreases membrane fluidity. Similarly, increasing the cholesterol content of membranes decreases membrane fluidity and can produce perturbations in cellular functions. For example, capping of surface immunoglobulins in lymphocytes, 8 platelet aggregability, 9 erythrcphagocytosis by macrophages, 10 and receptor binding of £-adrenergic, serotonine...

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Highly enriched, minimally disrupted plasma membrane vesicles from aortic myocytes grown in primary culture

Kattenburg

Stoclet

1984

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Plasma membrane vesicles prepared from unadhered monocytes: Characterization of calcium transport and the calcium ATPase

Cited by 16 publications

References 19 publications

Calcium exchange and ionized cytoplasmic calcium in resting and activated human monocytes.

Calcium exchange and ionized cytoplasmic calcium in resting and activated human monocytes.

Effect of dietary fat saturation and cholesterol on low density lipoprotein degradation by mononuclear cells of Cebus monkeys.

Highly enriched, minimally disrupted plasma membrane vesicles from aortic myocytes grown in primary culture

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