Protein tyrosine kinase activity in cultured vascular smooth muscle cells (VSMC) from rat aorta

1. Protein tyrosine kinase (PTK) activities were detected in both cytosolic and particulate fractions of cultured vascular smooth muscle cells by using poly (Glu: Tyr; 4:1) as an exogenous substrate. 2. The present distribution of the enzyme activity between these two fractions was 70 and 30 respectively. 3. The particulate and not the cytosolic enzyme activity was stimulated by about 4-fold in the presence of non-ionic detergent, Triton X-100 (0.5% v/v). 4. The PTK activity in both the fractions was absolutely dependent on the presence of divalent cations such as Mg2+ and Mn2+ which were equipotent in the activation of the enzyme. These data indicate that PTK activity is expressed in cultured VSMC and provide a basis for further studies to examine a possible role of PTKs in growth and proliferation of VSMC.