[One Chinese case of F V Leiden mutation associated with APC resistance].

OBJECTIVE: To investigate the Factor V Leiden mutation associated with activated protein C resistance (APCR) in Chinese. METHODS: Twenty-eight normal individuals and 18 patients with thrombotic diseases were studied by APC-APTT, PCR followed by Mnl I restriction enzyme analysis, PCR-SSP, and DNA sequence analysis. RESULTS: In one normal individual of Chinese origin, the APC sensitivity ratio (APC-SR) was found to be significantly lower than that in other normal controls. This individual was identified to be heterozygous for F V Leiden mutation (Arg506 --> Gln). The APC resistance was found in 3 other cases of thrombotic diseases, but with no F V Leiden mutation. CONCLUSION: This is the first case of F V Leiden mutation associated with APC resistance reported in Chinese. It is noteworthy whether other gene defects are associated with APC resistance in Chinese and in thrombotic diseases patients.

Activation of factors XII and VII induced in citrated plasma in the presence of contact surface.

Activated factor XII (XIIa), activated factor VII (VIIa) and factor VII coagulant activity (VIIc) were determined in non-treated and in treated (cold-incubated) citrated plasmas from women in late pregnancy and from norma volunteers. All three activities were higher in the non-treated plasmas from women in late pregnancy than from normal subjects. The incubation of citrated plasmas from women in late pregnancy, on ice for 24 hours, resulted in a many-fold increase of factor XIIa activity, factor VIIa levels and VIIc. The dilution of these plasmas resulted in a sharp decrease of all three activities in the post-incubation mixture, so that in the plasmas diluted 2:1 with buffer all three activities were similar to those in fresh plasmas. Similar incubations of diluted plasmas (1:1) from normal volunteers resulted in no increase of factor XIIa activity, factor VIIa levels and VIIc. However, the presence in the incubation mixture of micellar stearate resulted in a stearate concentration-dependent increase of all three activities in treated plasmas. Levels of factor XIIa activity and factor VIIa in the treated plasmas from both groups of subjects were highly correlated (r = 0.987; p < 0.001). There was also a highly significant correlation between VIIc and factor VIIa levels (0.989; p < 0.001). These results demonstrate that the in vitro increase in factor VIIa levels is due to the activation of the contact system of coagulation and is dependent on the potency of the contact surface. Moreover, VIIc over a wide range of values, observed in the present experiments, can provide an accurate measure of factor VIIa concentration.