ACTIVATION OF PLATELET HEPARITINASE BY VASCULAR CELL LYSATES

Tumour cells have been reported to contain an activator of platelet he paritinase which is absent from normal cells. Using an assay which mea sures the degradation of radiolabelled heparin, we observed that lysat es of metastatic melanoma cells did activate platelet heparitinase but that lysates of arterial endothelial and smooth muscle cells did like wise, with the latter being particularly effective. The activator larg ely survived a 10 min preincubation of the cell lysates at 70 degrees C, but not at 100 degrees C. Experimental results indicated that the c ontents of 10(5) vascular smooth muscle cells could increase platelet heparitinase activity in vitro to 6 times its initial value. We sugges t such activation may have physiological relevance and may even assist the development of certain cardiovascular diseases in man.