The human megakaryocytic cell line UT-7/TPO responds to platelet agonists with intracellular Ca2+ elevation and P-selectin expression.

Megakaryocytes have several signal transduction cascades that are similar, but not identical to platelet activation signals. In order to understand platelet signals in detail, it is useful to compare the similarities and/or differences between platelets and megakaryocytes. We evaluated platelet activation signals related to three kinds of Gq protein-coupled receptors using the megakaryocytic cell line UT-7/TPO. It was found that UT-7/TPO responded to thrombin, resulting in a continuous elevation of the [Ca2+]i (intracellular Ca2+) and P-selectin expression on the surface of the cells. Activation of integrin alpha Ilb beta 3 and thromboxane generation was not detected by any of the three stimulations. Taken together, although strong [Ca2+]i elevation by thrombin stimulation caused further P-selection expression, we could detect [Ca2+]i elevation, which is thought to be the individual signals through the thrombin, thromboxane A(2) or ADP receptor, without considering the secondary signalling caused by alpha Ilb beta 3 activation and the arachidonic acid cascade using UT-7/TPO.