Determination of the N-terminal amino acid sequence of the purified prothrombin from a patient with liver cirrhosis

Reference intervals for growth arrest-specific 6 protein in adults

The objective of this study was to establish reference intervals for growth arrest-specific 6 (GAS6), a vitamin K-dependent protein, in human adult plasma according to the Guideline of Clinical and Laboratory Standards Institute (CLSI) C28-A3. Blood samples were collected from 308 healthy volunteers aged 18-72 (157 female, 151 male). A non-parametric approach was used to calculate the reference interval. The plasma GAS6 reference interval was determined, with 90% confidence interval: the lower limit (2.5 percentile) was 2.5 (1.9-3.1) μg/L and the upper limit (97.5 percentile) = 18.8 (18.0-22.3) μg/L. Harris-Boyd's test did not suggest partitioning by age or gender: medians for males [7.8 (5.8-10.7) μg/L] and females [9.9 (7.1-13.5) μg/L]. Three age-subgroups were tested: 18-29 years (n = 168); 30-44 years (n = 73); 45-72 years (n = 67). The intra- and inter-assay variations were 12.6% (mean, 5.2 ± 0.7 μg/L) and 14.0% (mean, 9.2 ± 1.3 μg/L), respectively. The mean recovery was 104%. This study reports plasma GAS6 reference intervals established first according to the guideline of CLSI C28-A3.

Growth Arrest-Specific 6 (Gas6) and TAM Receptors in Mouse Platelets

Objective:

Growth arrest-specific 6 (Gas6) is a newly discovered vitamin K-dependent protein, which is a ligand for TAM receptors [Tyro3 (Sky), Axl, and Mer] from the tyrosine kinase family. Gas6 knockout mice were resistant to venous and arterial thrombosis. There are contradictory reports on the presence of Gas6 and its receptors in mouse platelets. The objective of this study was to investigate whether Gas6 and its receptors were present in mouse platelets or not.

Materials and Methods:

Specific pathogen-free BALB/c male and female mice of 8-10 weeks old and 25-30 g in weight were anesthetized under light ether anesthesia and blood samples were taken from their hearts. RNAs were isolated from isolated platelets, and then mRNAs encoding Gas6 and TAM receptors were detected by reverse transcription-polymerase chain reaction (RT-PCR). Protein concentrations of Gas6 and TAM receptors in platelets were measured by ELISA, but not those of Mer, because of the absence of any commercial ELISA kit for mouse specimens.

Results:

RT-PCR results indicated the presence of mRNAs encoding Gas6 and Mer in mouse platelets. However, although RT-PCR reactions were performed at various temperatures and cycles, we could not detect the presence of mRNAs encoding Axl and Tyro3 (Sky). Receptor protein levels of Axl and Tyro3 were below the detection limits of the ELISA method.

Conclusion:

We found the presence of mRNAs encoding Gas6 and the receptor Mer in mouse platelets, but not Axl and Tyro3. Gas6, Axl, and Tyro3 protein levels were below the detection limits of the ELISA. The presence of mRNA is not obvious evidence of protein expression in platelets that have no nucleus or DNA. Further studies are required to clarify the presence of Gas6/TAM receptors in platelets using real-time PCR and more sensitive immunological methods, and future studies on mechanisms will indicate whether the Gas6/TAM pathway is a strategy for treatment of disorders.

Research on PEGylation of porcine prothrombin for improving biostability and reducing animal immunogenicity

Prothrombin is a vitamin K-dependent serine protease and plays pivotal roles in both procoagulant and anticoagulant pathway of hemostasis. In this study, prothrombin purified from porcine plasma was modified through PEGylation at N-terminal residue using 40 kDa PEG-phenyl-isothiocyanate (PIT-PEG40K). The monoPEGylated prothrombin enhanced biostability and remarkably prolonged circulating half-life in mice as compared with that of the nonmodified prothrombin. Moreover, the immunogenicity of PEGylated prothrombin in mice is significantly decreased compared to nonmodified prothrombin. These studies demonstrated the feasibility of PEGylating prothrombin as a promising way for the development of new prothrombin drugs.

Avidin-biotin ELISA for measurement of prothrombin in human plasma

In this study, IgG was partially purified from rabbit antisera against human normal prothrombin. The presence of antibodies against prothrombin was shown by Ouchterlony's double immunodiffusion method. This IgG was adsorbed to microwells and an enzyme-linked immunosorbent assay (ELISA) method was developed by using biotinylated prothrombin. We used alkaline phosphatase as the labeling enzyme. Plasma prothrombin concentrations in 30 healthy individuals and 15 patients with liver cirrhosis were measured using this ELISA method. Prothrombin levels of the cirrhotic patients (61+/-36 microg/ml) were significantly lower than those of the control values (117+/-43 microg/ml) (P<.001). In addition to the ELISA method in the same samples, we assayed prothrombin levels by nephelometry and prothrombin activities using staphylocoagulase and chromogenic substrate. With nephelometry, in healthy individuals, a mean value of 104+/-17 microg/ml and, in cirrhotic patients, a mean value of 51+/-26 microg/ml of prothrombin levels were detected. The prothrombin activities were 10532+/-2429 and 2433+/-330 U/l, respectively. In both methods, the prothrombin values of cirrhotic patients were also significantly lower than those of the healthy individuals (P<.001). The correlation coefficient between ELISA and nephelometry was r=.90, P<.01, and between ELISA and the amidolytic assay was r=.69, P<.01. Prothrombin times (PT) of cirrhotic patients (18.5+/-2.3 s) were significantly longer and albumin (2.4+/-0.5 g/dl) levels were significantly lower than those of normal values (P<.001). PT were negatively correlated with prothrombin levels assayed by ELISA (r=-.59, P<.01). This enzyme immunoassay technique can be used to measure prothrombin levels in plasma.