INVESTIGATIONS ON MULTIMERIC STRUCTURE OF PLATELET VON WILLE-BRAND FACTOR IN PATIENTS WITH HEREDITARY DISORDERS OF PLATELET FUNCTION

Von Willebrand factor (vWF), a multimeric glycoprotein, plays an essential and multifunctional role in the hemostatic process. It is well known that platelet glycoproteins IB, IIB and IIIA contain receptors for vWF. Von Willebrand factor was also found in alpha granules of platelets. Therefore we investigated the multimeric structure of platelet vWF in 12 patients with different inherited disorders of platelet function. The patients had the following diagnosis: Hermansky Pudlak syndrome, Thrombasthenia and up to new undefined hereditary disorders of platelet function. The method is based upon:

1) washing of platelets 2) release of platelet vWF 3) separation of vWF multimers by SDS-agarose electrophoresis 4) subsequent blotting of vWF mul timers onto nitrocellulose 5) staining by peroxidase conjugated antibodies.

The investigations were repeated 3 times and compared to those of normal platelets. In 2 patients with Hermansky-Pudlak syndrane no multimeric structure could be detected in platelets whereas the multimeric pattern of plasma of these patients was normal. Also in one patient with the tentative diagnosis: thrombasthenia we couldn't find any multimeric structure in platelets compared to the normal multimeric composition of plasma. In 2 patients with giant platelets the multimeric distribution was normal. In the remaining 6 patients we observed multimeric structure which was different from that seen in vWd variants and in healthy volunteers. In 1 patient we found normal multimeric pattern in plasma and platelets.

Based on our findings it can be assumed that the analysis of multimeric structure of platelet vWF can be helpful for the diagnostic approach and for the insight in pathogenesis of inherited disorders of platelet function.