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Inhibition of the activation of Hageman factor (factor XII) by soluble human placental collagens types III, IV, and V.

The initial step in the formation of thrombin via the intrinsic pathway is the activation of Hageman factor (factor XII). Some, but not all, studies have shown that this activation may be brought about by collagen. We examined the effect of three types of soluble human placental collagen on Hageman factor. Collagen types III, IV, and V did not appear to activate Hageman factor under the conditions tested. To the contrary, these collagen species inhibited activation of Hageman factor by glass or ellagic acid. These studies suggest that some types of collagen may play an inhibitory role in blood coagulation.