Mechanized amidolytic technique for determination of factor X and factor-X antigen, and its application to patients being treated with oral anticoagulants.

Wijk, E. M. van; Kahlé, L.H.; Cate, J. W. Ten

doi:10.1093/clinchem/26.7.885

Cited by 34 publications

(15 citation statements)

References 5 publications

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“…Factor VII activity is reduced most rapidly in coumarin therapy. The rate of loss of the factor activities may be related to the half-life of the factors in the circu lation, 73 as indicated in Table 2. PT tests (thrombo plastins) that are overly sensitive to Factor VII levels may give misleading information in the early stages of anticoagulation.…”

Section: Extrinsic Pathway Assaysmentioning

confidence: 99%

See 1 more Smart Citation

Development and Clinical Use of Automated Synthetic Substrate Methods for the Evaluation of Coagulation and Fibrinolysis

Mitchell¹

1983

Semin Thromb Hemost

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Section: Extrinsic Pathway Assaysmentioning

confidence: 99%

“…Mibashan et al 48 73 investigated oral anticoagulant patient control with an automated Factor X assay.…”

Section: Factor Xa Substrate Assaysmentioning

confidence: 99%

Development and Clinical Use of Automated Synthetic Substrate Methods for the Evaluation of Coagulation and Fibrinolysis

Mitchell¹

1983

Semin Thromb Hemost

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“…Recently, a report described an automated amidolytic technique for the determination of Factor X and Factor X antigen in patients treated with oral anticoagulant drugs. 45 Patients receiving oral anticoagulants had significantly lower factor levels utilizing thromboplastin or Russell's viper venom activation than was found by assaying for antigen. Although the Factor X antigen levels were decreased in this group of patients, they were much higher than the Factor X coagulant or amidolytic activities.…”

mentioning

confidence: 93%

Newer Synthetic Peptide Substrates in Coagulation Testing: Some Practical Considerations for Automated Methods

Svendsen¹,

Fareed²,

Walenga³

et al. 1983

Semin Thromb Hemost

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“…Monitoring of anticoagulant treatment, including Factor X methods, has been carried out in at least ten different countries. 5 ' 6 ' 9 ' 20 ' 36 " 38 ' 62 ' 76 ' 77 ' 79 ' 85 ' 100,108 The conditions used in the assays are very similar. Optimization data and the method control data obtained in our laboratory prove that the minor differences are of no significance.…”

Section: Methods For the Assay Of Factor X Using Rvv And The Substratmentioning

confidence: 99%

Synthetic Peptide Substrate Assays in Coagulation and Fibrinolysis and Their Application on Automates

Friberger¹

1983

Semin Thromb Hemost

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The mammalian proteolytic network involving coagulation, fibrinolytic, kallikrein-kinin, and complement systems is built with inactive zymogens, regulated by activators and inhibitors and by positive as well as negative feedback control mechanisms. They are connected to each other in several ways (Fig. 1). There are a number of components in in blood and vessel tissues that regulate these events.The large number of factors and their numerous points of interaction make their quantitation very difficult. The interpretation of the results obtained is also complicated by the complexity of the systems in question. It was therefore a great step forward when a number of specific synthetic substrates, mainly chromogenic, for protease assays were introduced.A brief description of the biochemistry of the synthetic substrate is included in this article. By utilizing the existing knowledge of the protease systems and considering the different precautions that must be taken, specific methods have been designed. The automation of these methods is then rather a straightforward task. Some principles are discussed here, but each type of equipment has its own characteristic properties. SYNTHETIC PEPTIDE SUBSTRATES Natural Substrates Versus Synthetic SubstratesThe proteases regulating coagulation, fibrinolysis, and other systems (Fig. 1) generally act specifically toward their natural substrates. These substrates are, however, difficult to isolate. The assays in which they are used are often cumbersome and the results are difficult to evaluate. For this reason "the first generation" of synthetic substrates, simple amino acid esters (for example tosoylarginine-methyl ester and benzoyl-arginine-ethyl ester), were introduced. In order to make the assays more simple and sensitive, chromogenic single amide substrates (for example, benzoyl-arginine-pnitroanilide) were developed.A "second generation" of synthetic substrates was born when the single amino acid was exchanged for short peptide chains that primarily were designed to mimic the natural substrate (Fig. 2). Thus it was possible to use affinity sites near the active site of the natural substrate. This was the beginning of more extensive clinical applications of synthetic substrates. The principle of the assay of proteases with a chromogenic tripeptide substrate is shown in Figure 3.The rate at which p-nitroaniline (pNA) is released is measured photometrically at 405 nm, and A A/minute is proportional to the enzyme activity (Michaelis-Menton kinetics). The ultraviolet absorbance curves of intact substrate and of free pNA are shown in Figure 4. The absorbance of the substrate and product at different wavelengths is given in Table 1.Spatial conformation and charge distribution of the substrates are important for the enzyme to recognize its substrate. Some affinity sites of the enzymes may be situated at a distance from the active site (where the reaction takes place) and do not influence the reaction with small molecular weight substrates. This may, on the one hand, be

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Mechanized amidolytic technique for determination of factor X and factor-X antigen, and its application to patients being treated with oral anticoagulants.

Cited by 34 publications

References 5 publications

Development and Clinical Use of Automated Synthetic Substrate Methods for the Evaluation of Coagulation and Fibrinolysis

Development and Clinical Use of Automated Synthetic Substrate Methods for the Evaluation of Coagulation and Fibrinolysis

Newer Synthetic Peptide Substrates in Coagulation Testing: Some Practical Considerations for Automated Methods

Synthetic Peptide Substrate Assays in Coagulation and Fibrinolysis and Their Application on Automates

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