Inhibition of lymphoproliferation by dipyridamole

Dipyridamole (DP, Persantin) was examined for its effects on the proliferation of mitogen-stimulated murine splenocytes and L1210 leukemia cells. In keeping with its reported activity as an inhibitor of nucleoside transport, DP inhibited incorporation by lymphoid cells of labeled thymidine and uridine into macromolecules. That this inhibition resulted from activities in addition to suppression of nucleoside transport was verified by measured decreases of cellular DNA and viable cell numbers. In addition, protein synthesis was also decreased as indicated by labeled valine incorporation and total protein content of the cells. The rapid accumulation of cAMP in phytohemagglutinin-stimulated splenocytes in the presence of DP may provide an explanation for the anti-proliferative effect of DP on lymphoid cells.