There are scarce reports about the effects on haemostasis in mammals chronically exposed to extremely low frequency magnetic fields. The goal of this study was to evaluate the variations on blood coagulation and fibrinolysis parameters of OF1 mice chronically exposed to a magnetic field of 50Hz, 15mT (rms). Parental mice were exposed to a magnetic field during 98 days. Mating, pregnancy, lactation, and development of the progeny until it was 220 days old, were carried out under the experimental field. Control groups were maintained under the same experimental conditions but exclusively exposed to a local geomagnetic field. The study was carried out over: 35 control female mice, 50 exposed female mice, 35 control male mice, and 51 exposed male mice. PT, APTT, fibrinogen dosage, RT, and factor VIII, plasminogen and PAI-1 activities were performed using platelet-poor plasma, whereas t-PA activity was assayed in whole blood. Experimental results were analysed by SPSS and expressed as mean value ± standard deviation. ANOVA of one and two ways and Scheffé's test were applied to evaluate statistical differences in data.

A clear difference sex-related was seen. Thus, male mice showed more capacity to coagulate and a less active fibrinolysis than female mice of both control and exposed animals. The increase of exposed female mice coagulability seems to be associated with magnetic field applied when compared with control group values. Results of fibrinolysis assays suggest a decrease of fibrinolytic potential associated to magnetic field exposure, relevant exclusively in male mice.