Effect of thrombin and thrombin receptor agonist peptide on p42-44 MAPK tyrosine phosphorylation in different Jurkat clones. Cells were stimulated for the times indicated with 100 nmol/L thrombin (A) or 2.5 μmol/L thrombin receptor agonist peptide (B). Proteins from cell lysates were separated by SDS-PAGE and transferred to Immobilon membranes for Western blotting with phospho-specific p42-44 MAPK antibody. Development was performed as described in Fig 1.