The Phosphatase Inhibitor Calyculin-A Impairs Clot Retraction, Platelet Activation, and Thrombin Generation

Figure 6

Changes of the cytosolic Ca²⁺ level of platelet groups in relation to activation by thiomersal in Ca²⁺-free buffer and the consequent store-operated calcium entry. Thiomersal evoked a prolonged elevation of cytosolic calcium in all the platelets followed by sustained store-operated calcium entry (a). Nonactivated platelets kept in calcium-free buffer show a minimal calcium entry in response to the resupplement of extracellular calcium by calcium chloride, probably due to platelets that got activated on physical contact to the glass coverslip (b). Thiomersal evoked a prolonged elevation of cytosolic calcium in CLA-pretreated platelets followed by sustained store-operated calcium entry, similarly to the response seen in NA platelets (c). All preparations responded to calcium ionophore A23187 with an increased calcium level. All curves are values where an increase indicates higher cytosolic calcium levels. Arrows mark the addition of thiomersal.

(a)

(b)

(c)