Endothelin-1 Effect on Tyrosine Phosphorylation and on Tyrosine Phosphatase (PTP-1C) Translocation in Rabbit Platelets

This study examined the temporal relationships of endothelin-1-stimulated rabbit platelets tyrosine phosphorylated proteins. The effect of endothelin-1 on tyrosine phosphorylation was dose- and time-dependent and caused a rapid tyrosine phosphorylation of three groups of proteins in the molecular mass range 70-100 kDa, 100-150 kDa and 150-200 kDa. Significant protein tyrosine phosphatase activity and amount were found to be associated with the cytoskeleton of endothelin-1-stimulated rabbit platelets. Under our experimental conditions, translocation from the cytosolic fraction to the cytoskeleton reached its highest levels within 10-20 sec of endothelin-1 stimulation. Endothelin-1-induced translocation of protein tyrosine phosphatase, associated with the increase in its activity was demonstrated by immunoblotting and immunoelectron microscopy.