Effects of dipyridamole in vivo on ATP and cAMP content in platelets and arterial walls and on atherosclerotic plaque formation.

In rabbits receiving an atherogenic diet for 2 months, the ATP content of platelet rich plasma (PRP) and arterial tissue was significantly elevated as compared to normal rabbits. This increase in ATP levels of platelets from atherosclerotic rabbits was paralleled by higher basal as well as PGI2-induced cAMP levels. In arterial tissues, an increase was only obtained in PGI2-stimulated cAMP content. Treatment with dipyridamole (DPD) for 4 weeks resulted in a reduction of the ATP content in platelets and arterial tissue from atherosclerotic rabbits to values seen in normal animals. Again, the reduction of ATP content was reflected in a decrease of basal as well as PGI2-induced cAMP levels in platelets, whereas in arterial tissue a decrease was only obtained in PGI2-induced cAMP content. At the same time, DPD treatment enhanced atherosclerotic plaque formation in the aortic wall. The enhanced atherosclerotic plaque formation seen in DPD treated atherosclerotic rabbits may be linked to the inhibition of adenosine uptake, resulting in a decrease of the adenine nucleotide pools of arterial wa-l cells. The decrease also caused a reduction in PGI2-induced cAMP content. This effect may be linked to altered proliferative activity, since in many cell types, stimulation of cAMP levels results in reduced proliferation rates.