The acute release of tissue-type plasminogen activator (t-PA) activity and of von Willebrand Factor (vWF) antigen from vascular endothelium was studied ex vivo using the rat hindquarter isolated perfusion model. The release of these proteins has been reported to occur simultaneously in response to a variety of endothelial cell agonists including bradykinin, thrombin and platelet activating factor. It has therefore been suggested that similar endothelial cell pathways and mechanisms are involved in the release of t-PA and vWF in vivo. This paper shows that the releases of t-PA and of vWF are not always closely linked and may depend on the agonist utilized to effect release. In our hands, the bradykinin-induced release of these proteins appears to be essentially identical, but this is not true for adenosine diphosphate (ADP). Rather, ADP is capable of causing the acute release of t-PA without the simultaneous release of vWF in the ex vivo rat hindquarter model. This indicates that the bradykinin- and ADP-induced pathways for t-PA release are probably distinct and that the releases of t-PA and vWF are not as closely linked as previously believed.
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Smalley et al. (1993) studied this question.