Platelet-polymer interactions: morphologic and intracellular free calcium studies of individual human platelets

Light and electron microscopic methods were used to correlate changes in platelet morphology with levels of internal free calcium in platelets adhering to Formvar, Pellethane, and 14% SO3 Pellethane. Free calcium levels were elevated when platelets initially activated in response to contact with the polymer substrates. With buffer containing 1 mM CA2+, representative of in vivo plasma calcium levels, platelets activating on the sulfonated substrate exhibited significantly higher intracellular free calcium levels compared to those on Formvar and Pellethane. Furthermore, the intracellular free calcium remained elevated in these platelets which failed to spread normally on the sulfonated substrate. In contrast, the platelets adherent on Formvar and Pellethane achieved normal fully spread morphologies with correspondingly low or resting calcium levels. Our results indicate that the addition of the sulfonated group to Pellethane affected internal platelet calcium regulation to cause an abnormal spreading response. The nonviable platelet morphologies observed on sulfonated Pellethane compare to other dead cell morphologies caused by abnormally elevated levels of intracellular free Ca2+.