Vasodilator effect of thrombins prepared from normal or deficient human or canine plasmas

Thrombins prepared from plasmas deficient in various clotting factors are capable of inducing vasodilator response to the hindlimb of the dog and this response proved to be similar to that produced by thrombins prepared from normal plasmas. Thus the vascular effect of thrombin is not mediated by any other clotting factor which might be present in small amounts in the thrombin preparations. Thrombin prepared from canine normal plasma exerted a more potent vasodilator response, indicating a species specificity for the vascular response to thrombin. Since the vasodilating effect of thrombin is not mediated by (i) a nervous mechanism, (ii) any known vasodilating substance or (iii) any other clotting factor, it is concluded that the thrombin moiety possesses vasodilating properties.