Calpain rapidly cleaves talin in stimulated platelets in the absence of αIIbβ3 activation and cytoskeleton-generated force. Unstirred suspensions of washed human platelets were preincubated with either buffer (unstimlated platelets), 1 mM of eptifibatide, 1 mM of ALLN, 1 mM of ALLM, 2 μM of blebbistatin, or 2 μM of latrunculin for 15 minutes at 37°C. An aliquot of the resting platelets and platelets that had been preincubated with eptifibatide, ALLN, ALLM, blebbistatin, or latrunculin A were then stimulated with either 5 units/mL of thrombin (Tb) or SFLLRN as indicated without stirring for 5 minutes at 37°C, after which they were lysed and the lysate immunoblotted with TA205.