Sulfatide prolongs blood-coagulation time and bleeding time by forming a complex with fibrinogen.

Sulfatides (galactosylceramide I3-sulfate), which are found in serum lipoproteins of various mammals, effectively increased prothrombin time (anticoagulant effect) and also effectively prolonged bleeding time (anti-platelet effect). When equal volumes of a homogeneous micellar solution of sulfatide and fibrinogen in phosphate-buffered saline were mixed, an insoluble complex precipitated. Analysis of the precipitated complex showed that the molar ratio of sulfatide to fibrinogen was about 400:1. These results indicate that the sulfatide micelle binds tightly to fibrinogen and thereby interferes with both fibrin gel formation (anticoagulant activity) and platelet function.