Regulation of JNK1 and ERK2 activation. (A) JNK1 and ERK2 activation in stirred and unstirred platelets in the presence or absence of RGDS peptide. Washed platelets were preincubated with or without RGDS peptide (1 mmol/L) for 30 seconds and stimulated with thrombin (0.2 U/mL) for various times, in the presence or absence of stirring (+ stirring and + RGDS, ▪; + stirring and − RGDS, □; − stirring and + RGDS, •; − stirring and − RGDS, ○). The JNK1 phosphorylation (JNK1) and ERK2 phosphorylation (ERK2) of the lysates were then assessed. Autoluminographs were scanned with a laser densitometer. For each experiment, the ratio of phosphorylated JNK1 and ERK2 was normalized to that of stirred platelets treated with thrombin alone (2 minutes) expressed as a relative intensity. Results are the means ± SEM for four experiments. (B) Effect of stirring on thrombin-induced JNK1 and ERK2 activation in a thrombasthenic patient. Stirred and unstirred platelets from Glanzmann’s thrombasthenia patient were stimulated with thrombin (0.2 U/mL) for various times. The JNK1 phosphorylation and ERK2 phosphorylation and total JNKs and ERKs of the lysates were investigated.