The risk of venous thrombosis is known to increase when the protein concentration of blood is increased as in dehydration. However, the effect of protein concentration on arterial thrombosis is still unclear. We have investigated von Willebrand factor (vWF)-dependent, shear-induced platelet aggregation in the presence of varying concentrations of fovine serum albumin (BSA) as well as in platelet count-controlled platelet-rich plasma obtained before and after the intake of 1, 000ml of isotonic water. Washed platelet suspension in the presence of 5, 25 and 50mg/ml of BSA and platelet-rich plasma separated from blood obtained from 11 normal volunteers before and after the water intake were exposed to a relatively low (1, 200s^-1), intermediate (7, 200s^-1), and high (10, 800s^-1) shear rate for six minutes. The extent of shear-induced platelet aggregation was measured with an optically modified cone-plate viscometer.
The extent of platelet aggregation occurring under a relatively high shear rate of 10, 800s^-1 was increased from 43.1±4.0 to 50.4±5.4% after water intake although those occurring under intermediate and low shear rates did not change significantly. The results with washed platelet suspension also indicated that platelet aggregation occurring under a high shear rate was increased with a lower concentration of BSA. These results suggested that vWF-mediated shear-induced platelet aggregation, which might be relevant to the onset of arterial thrombosis, was inhibited by the presence of higher concentration of plasma proteins, and that unlike venous thrombosis, dehydration is a risk factor for arterial thrombosis including coronary thrombosis.

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Normal prothrombin, i.e., fully γ-carboxylated prothrombin in plasma is now measurable by a chromogenic assay using carinactivase-1 (CA-1) isolated from the Echis carinatus leucogaster venom. This enzyme has been shown to solely activate fully γ-carboxylated prothrombin but not so-called PIVKA-II lacking one or more γ-carboxyglutamic acids in the prothrombin molecule. The plasma level of normal prothrombin was determined by the chromogenic assay utilizing this enzyme in 10 patients who had undergone heart surgery and had been treated with warfarin postoperatively. Plasma samples were collected from day 4 to day 20 after surgery and the data were compared with the values of thrombotest (TT) and the prothrombin time-international normalized ratio (PT-INR).
The level of normal prothrombin decreased in all patients after initiation of the warfarin therapy, and the extent of the decrease was found to correlate with TT positively, but with PT-INR negatively. Since the CA-1 method can be conducted very rapidly and requires only a small amount of plasma, this method is expected to be clinically utilized for monitoring the warfarin therapy after appropriate improvement in the assay system.

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In two patients, a 36-year-old woman (patient 1) and a 27-year-old man (patient 2), with a history of prolonged, massive bleeding after trauma and/or surgery, we have identified a heterozygous nucleotide exchange of G to A at different positions 1334 and 1340 of the gene for plasminogen activator inhibitor-1 (PAI-1) by single strand conformation polymorphism followed by direct nucleotide sequencing. The G1334A exchange has already been reported to be a polymorphism, but G1340A has not been reported heretofore. These positions correspond to the region encoding the signal peptide of PAI-1, and the nucleotide exchanges necessitate to translate Thr for Ala at position -9 and Ile for Val at position-7, respectively. Since these patients were found to have decreased levels of activity and antigen of PAI-1 in plasma, 12.1U/ml and 9.0ng/ml in patient 1 and 4.1U/ml and 1.8ng/ml in patient 2 (control: 15.0±8.0U/ml and 16.7±7.5ng/ml), respectively, we attempted to see whether these nucleotide enchanges were relevant to the bleeding tendencies by analyzing the relationship between the phenotype (the plasma PAI-1 levels) and the genotype in 30 normal subjects. The genotype of 1334G/A was identified in 6 subjects but none of them were found to have decreased levels of PAI-1. On the other hand, that of 1340G/A was found only in a single subject. Thus the genotype 1334G/A may not be related to the decreased PAI-1 in plasma, whereas the relevance of genotype 1340G/A to the PAI-1 decrease was not decisively clarified. By further analysis of the PAI-1 gene in another 200 healthy subjects, the frequencies for G and A at position 1334 were found to be 0.91 and 0.09, respectively, and for those at positions 1340 were 0.98 and 0.02, respectively.

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