Methods for the Detection of Activated Platelets

Pareti, F. I.; D’Angelo, Armando; Mannucci, Pier Mannuccio

doi:10.1007/978-1-4684-8616-2_16

Advances in Experimental Medicine and Biology

1984

DOI: 10.1007/978-1-4684-8616-2_16

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Methods for the Detection of Activated Platelets

F. I. Pareti

Armando D’Angelo

Pier Mannuccio Mannucci

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1985

1987

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Cited by 3 publications

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“…Techniques ("-g) have shown that platelets from patients with thrombosis and vascular occlusive diseases can be activated with lower levels of activators and can aggreg ate at higher rates than normal controls (2,17,(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). The present communication makes a quantitative study of these phenomena.…”

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confidence: 75%

Abnormal Aggregation Accompanies Abnormal Platelet Ca2+ Handling in Arterial Thrombosis

Shanbaky

Ahn

et al. 1987

Thromb Haemost

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SummaryThe resting levels of cytoplasmic Ca2+ (measured by Quin 2 fluorescence) and dense tubular Ca2+ (measured by chlorotetracycline, CTC, fluorescence) are shown to be higher in platelets from patients with arterial thrombosis than from normal donors. Turbidmetric studies of aggregation of diluted platelet-rich plasma (PRP) at 135 μM Ca2+ showed increased rates of aggregation for patients relative to normal controls. For ADP-stimulated aggregation, increased maximal rates (Vmax) and decreased doses for half-maximal rates were observed. With collagen-stimulated aggregation, patient samples showed only decreased ED50 values relative to normal controls. The changes in these values are linearly correlated with the elevation of resting dense tubular Ca2+ level determined by the calcium-CTC test carried out at 2 mM external Ca2+. For ADP-stimulated aggregation this relationship can be mimicked by pre-incubating normal platelets with subcritical concentrations of the Ca2+ ionophore A23187.These results suggest that elevated cytoplasmic and dense tubular Ca2+ in the “resting state” is a major factor in arterial thrombosis, rendering the platelet more sensitive to the stimulation by physiologic agents.

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mentioning

confidence: 75%

Abnormal Aggregation Accompanies Abnormal Platelet Ca2+ Handling in Arterial Thrombosis

Shanbaky

Ahn

et al. 1987

Thromb Haemost

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Drug-related changes in platelet shape in whole blood

Rosenstein

1985

Thrombosis Research

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Abnormal calcium handling by platelets in thrombotic disorders.

Jy¹,

Ahn²,

Shanbaky³

et al. 1987

Circulation Research

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This study presents a quantitative comparison of the free cytoplasmic calcium concentration ([Ca2+]cyt) and the free concentration in the lumen of the dense tubules of the human platelet. The former was measured by the fluorescence of the high affinity indicator quin2 and latter by the fluorescence of chlorotetracycline (CTC). The CTC technique monitors calcium-CTC complex accumulation in the lumen of dense tubules and mitochondria when washed platelets were incubated in 2 mM Ca2+. Resting cytoplasmic and dense tubular Ca2+ concentrations were studied in platelets from patients suffering from venous and arterial thrombosis. Compared with normal controls (0.40 +/- 0.10, n = 54), the values of the calcium-CTC ratios were 0.68 +/- 0.19 (n = 16, p less than 0.005) in venous thrombosis; 0.75 +/- 0.18 (n = 14, p less than 0.005) in cardiovascular accident; 0.84 +/- 0.18 (n = 6, p less than 0.005) in occlusive peripheral vascular diseases; and 0.42 +/- 0.10 (n = 21, p greater than 0.1) in patient controls. The dense tubular Ca2+ levels for both patients and controls were perfectly correlated with the cytoplasmic levels using an equation that assumes that the dense tubular free calcium concentration ([Ca2+]dt) has a second power dependence on [Ca2+]cyt. The abnormal Ca2+ handling of platelets obtained from thrombotic patients could be completely reversed by preincubation with the calcium channel blocker verapamil. These observations suggest that the primary Ca2+ handling defect is the leakage through activated channels in the plasma membrane. The defect and the elevated resting [Ca2+]cyt and [Ca2+]dt are adequate to explain the observation of increased rates of collagen-activated aggregation in the above-mentioned group of patients. The results can be explained by platelets from thrombosis patients being exposed to activating factors in the circulation, resulting in Ca2+ channel activation. Channel activation persists through the process of platelet isolation and washing and is manifested in higher measured values of [Ca2+]cyt and [Ca2+]dt in the "resting state." This would bring the platelet closer to its aggregation when aggregation-inducing agents are added. The CTC test is shown to be a useful and convenient means of detecting this abnormality.

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Methods for the Detection of Activated Platelets

Cited by 3 publications

References 61 publications

Abnormal Aggregation Accompanies Abnormal Platelet Ca2+ Handling in Arterial Thrombosis

Abnormal Aggregation Accompanies Abnormal Platelet Ca2+ Handling in Arterial Thrombosis

Drug-related changes in platelet shape in whole blood

Abnormal calcium handling by platelets in thrombotic disorders.

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