Electric sizing of platelets stimulated by adenosine diphosphate (ADP).

The platelet-rich plasma stimulated by a low dose of adenosine diphosphate (ADP) was examined by an electric counter, oscilloscopy, an electron microscopy and packed cell volume analysis. The size distribution curve obtained by the electric counter shifted to the left, and the cell volume was decreased. On the oscillograph, those small cells were seen as pulse signals with a regular shape. However, microscopic observation did not find as many microplatelets or fragments. Also, packed cell volume analysis showed no difference between ADP-stimulated and unstimulated samples. On the electronmicrograph, a slight aggregation was seen, with many of the ADP-stimulated platelets exhibiting spiny forms. The shape factors influences strongly the electric sizing, thus, the deformation of platelets may be the reason for the disagreement between the results by electric observation and those by other methods. Our results indicated that the small platelets observed on the size distribution curve do not always reflect the actual small cells.