Effect of thrombin and thrombin receptor agonist peptide on p38 MAPK tyrosine phosphorylation. 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 subjected to SDS-PAGE as described above and transferred to Immobilon membranes for Western blotting using phospho-specific p38 MAPK antibody. Equal amounts of p38 MAPK were detected in each condition (C). Densitometric scanning of the p38 phosphorylated band present in (A) (thrombin-stimulated Jurkat clones) and (B) (thrombin receptor agonist peptide stimulated Jurkat clones) are shown. Results are representative of three experiments.